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sqrt(1-2x)=a-7absolute(x) equation

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Numerical solution:

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The solution

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  _________            
\/ 1 - 2*x  = a - 7*|x|
$$\sqrt{1 - 2 x} = a - 7 \left|{x}\right|$$
Detail solution
For every modulo expressions in the equation
allow cases, when this expressions ">=0" or "<0",
solve the resulting equation.

1.
$$x \geq 0$$
or
$$0 \leq x \wedge x < \infty$$
we get the equation
$$- a + 7 x + \sqrt{1 - 2 x} = 0$$
after simplifying we get
$$- a + 7 x + \sqrt{1 - 2 x} = 0$$
the solution in this interval:
$$x_{1} = \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49}$$
$$x_{2} = \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49}$$

2.
$$x < 0$$
or
$$-\infty < x \wedge x < 0$$
we get the equation
$$- a + 7 \left(- x\right) + \sqrt{1 - 2 x} = 0$$
after simplifying we get
$$- a - 7 x + \sqrt{1 - 2 x} = 0$$
the solution in this interval:
$$x_{3} = - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49}$$
$$x_{4} = - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49}$$


The final answer:
$$x_{1} = \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49}$$
$$x_{2} = \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49}$$
$$x_{3} = - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49}$$
$$x_{4} = - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49}$$
The graph
Sum and product of roots [src]
sum
    //             ___________                 ___   __________    \     //             ___________                 ___   __________    \       //             ___________                 ___   __________    \     //             ___________                 ___   __________    \       //         ___________                     ___   __________     \     //         ___________                     ___   __________     \       //             ___________                   ___   __________     \     //             ___________                   ___   __________     \
    ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |     ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |       ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |     ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |       ||  1    \/ 50 - 14*a    a      1    a   \/ 2 *\/ 25 - 7*a      |     ||  1    \/ 50 - 14*a    a      1    a   \/ 2 *\/ 25 - 7*a      |       ||  1    a   \/ 50 - 14*a         1    a   \/ 2 *\/ 25 - 7*a      |     ||  1    a   \/ 50 - 14*a         1    a   \/ 2 *\/ 25 - 7*a      |
    ||- -- - - - -------------  for -- + - + ------------------ > 0|     ||- -- - - - -------------  for -- + - + ------------------ > 0|       ||- -- - - + -------------  for -- + - - ------------------ > 0|     ||- -- - - + -------------  for -- + - - ------------------ > 0|       ||- -- - ------------- + -  for -- - - + ------------------ <= 0|     ||- -- - ------------- + -  for -- - - + ------------------ <= 0|       ||- -- + - + -------------  for - -- + - + ------------------ >= 0|     ||- -- + - + -------------  for - -- + - + ------------------ >= 0|
I*im|<  49   7         49           49   7           49            | + re|<  49   7         49           49   7           49            | + I*im|<  49   7         49           49   7           49            | + re|<  49   7         49           49   7           49            | + I*im|<  49         49        7      49   7           49             | + re|<  49         49        7      49   7           49             | + I*im|<  49   7         49             49   7           49             | + re|<  49   7         49             49   7           49             |
    ||                                                             |     ||                                                             |       ||                                                             |     ||                                                             |       ||                                                              |     ||                                                              |       ||                                                                |     ||                                                                |
    ||          nan                          otherwise             |     ||          nan                          otherwise             |       ||          nan                          otherwise             |     ||          nan                          otherwise             |       ||          nan                          otherwise              |     ||          nan                          otherwise              |       ||          nan                           otherwise               |     ||          nan                           otherwise               |
    \\                                                             /     \\                                                             /       \\                                                             /     \\                                                             /       \\                                                              /     \\                                                              /       \\                                                                /     \\                                                                /
$$\left(\left(\left(\operatorname{re}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}\right) + \left(\operatorname{re}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}\right)\right) + \left(\operatorname{re}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}\right)\right) + \left(\operatorname{re}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}\right)$$
=
    //             ___________                 ___   __________    \       //             ___________                 ___   __________    \       //         ___________                     ___   __________     \       //             ___________                   ___   __________     \     //             ___________                 ___   __________    \     //             ___________                 ___   __________    \     //         ___________                     ___   __________     \     //             ___________                   ___   __________     \
    ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |       ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |       ||  1    \/ 50 - 14*a    a      1    a   \/ 2 *\/ 25 - 7*a      |       ||  1    a   \/ 50 - 14*a         1    a   \/ 2 *\/ 25 - 7*a      |     ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |     ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |     ||  1    \/ 50 - 14*a    a      1    a   \/ 2 *\/ 25 - 7*a      |     ||  1    a   \/ 50 - 14*a         1    a   \/ 2 *\/ 25 - 7*a      |
    ||- -- - - - -------------  for -- + - + ------------------ > 0|       ||- -- - - + -------------  for -- + - - ------------------ > 0|       ||- -- - ------------- + -  for -- - - + ------------------ <= 0|       ||- -- + - + -------------  for - -- + - + ------------------ >= 0|     ||- -- - - - -------------  for -- + - + ------------------ > 0|     ||- -- - - + -------------  for -- + - - ------------------ > 0|     ||- -- - ------------- + -  for -- - - + ------------------ <= 0|     ||- -- + - + -------------  for - -- + - + ------------------ >= 0|
I*im|<  49   7         49           49   7           49            | + I*im|<  49   7         49           49   7           49            | + I*im|<  49         49        7      49   7           49             | + I*im|<  49   7         49             49   7           49             | + re|<  49   7         49           49   7           49            | + re|<  49   7         49           49   7           49            | + re|<  49         49        7      49   7           49             | + re|<  49   7         49             49   7           49             |
    ||                                                             |       ||                                                             |       ||                                                              |       ||                                                                |     ||                                                             |     ||                                                             |     ||                                                              |     ||                                                                |
    ||          nan                          otherwise             |       ||          nan                          otherwise             |       ||          nan                          otherwise              |       ||          nan                           otherwise               |     ||          nan                          otherwise             |     ||          nan                          otherwise             |     ||          nan                          otherwise              |     ||          nan                           otherwise               |
    \\                                                             /       \\                                                             /       \\                                                              /       \\                                                                /     \\                                                             /     \\                                                             /     \\                                                              /     \\                                                                /
$$\operatorname{re}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + \operatorname{re}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + \operatorname{re}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + \operatorname{re}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
product
/    //             ___________                 ___   __________    \     //             ___________                 ___   __________    \\ /    //             ___________                 ___   __________    \     //             ___________                 ___   __________    \\ /    //         ___________                     ___   __________     \     //         ___________                     ___   __________     \\ /    //             ___________                   ___   __________     \     //             ___________                   ___   __________     \\
|    ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |     ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     || |    ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |     ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     || |    ||  1    \/ 50 - 14*a    a      1    a   \/ 2 *\/ 25 - 7*a      |     ||  1    \/ 50 - 14*a    a      1    a   \/ 2 *\/ 25 - 7*a      || |    ||  1    a   \/ 50 - 14*a         1    a   \/ 2 *\/ 25 - 7*a      |     ||  1    a   \/ 50 - 14*a         1    a   \/ 2 *\/ 25 - 7*a      ||
|    ||- -- - - - -------------  for -- + - + ------------------ > 0|     ||- -- - - - -------------  for -- + - + ------------------ > 0|| |    ||- -- - - + -------------  for -- + - - ------------------ > 0|     ||- -- - - + -------------  for -- + - - ------------------ > 0|| |    ||- -- - ------------- + -  for -- - - + ------------------ <= 0|     ||- -- - ------------- + -  for -- - - + ------------------ <= 0|| |    ||- -- + - + -------------  for - -- + - + ------------------ >= 0|     ||- -- + - + -------------  for - -- + - + ------------------ >= 0||
|I*im|<  49   7         49           49   7           49            | + re|<  49   7         49           49   7           49            ||*|I*im|<  49   7         49           49   7           49            | + re|<  49   7         49           49   7           49            ||*|I*im|<  49         49        7      49   7           49             | + re|<  49         49        7      49   7           49             ||*|I*im|<  49   7         49             49   7           49             | + re|<  49   7         49             49   7           49             ||
|    ||                                                             |     ||                                                             || |    ||                                                             |     ||                                                             || |    ||                                                              |     ||                                                              || |    ||                                                                |     ||                                                                ||
|    ||          nan                          otherwise             |     ||          nan                          otherwise             || |    ||          nan                          otherwise             |     ||          nan                          otherwise             || |    ||          nan                          otherwise              |     ||          nan                          otherwise              || |    ||          nan                           otherwise               |     ||          nan                           otherwise               ||
\    \\                                                             /     \\                                                             // \    \\                                                             /     \\                                                             // \    \\                                                              /     \\                                                              // \    \\                                                                /     \\                                                                //
$$\left(\operatorname{re}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}\right) \left(\operatorname{re}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}\right) \left(\operatorname{re}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}\right) \left(\operatorname{re}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}\right)$$
=
/      4        4          2          2          2      2            3                                    3                                    
|1 + im (a) + re (a) - 2*re (a) + 2*im (a) - 6*im (a)*re (a) - 4*I*im (a)*re(a) - 4*I*im(a)*re(a) + 4*I*re (a)*im(a)                           
|-------------------------------------------------------------------------------------------------------------------  for And(a <= 25/7, a > 1)
<                                                        2401                                                                                  
|                                                                                                                                              
|                                                        nan                                                                  otherwise        
\                                                                                                                                              
$$\begin{cases} \frac{\left(\operatorname{re}{\left(a\right)}\right)^{4} + 4 i \left(\operatorname{re}{\left(a\right)}\right)^{3} \operatorname{im}{\left(a\right)} - 6 \left(\operatorname{re}{\left(a\right)}\right)^{2} \left(\operatorname{im}{\left(a\right)}\right)^{2} - 2 \left(\operatorname{re}{\left(a\right)}\right)^{2} - 4 i \operatorname{re}{\left(a\right)} \left(\operatorname{im}{\left(a\right)}\right)^{3} - 4 i \operatorname{re}{\left(a\right)} \operatorname{im}{\left(a\right)} + \left(\operatorname{im}{\left(a\right)}\right)^{4} + 2 \left(\operatorname{im}{\left(a\right)}\right)^{2} + 1}{2401} & \text{for}\: a \leq \frac{25}{7} \wedge a > 1 \\\text{NaN} & \text{otherwise} \end{cases}$$
Piecewise(((1 + im(a)^4 + re(a)^4 - 2*re(a)^2 + 2*im(a)^2 - 6*im(a)^2*re(a)^2 - 4*i*im(a)^3*re(a) - 4*i*im(a)*re(a) + 4*i*re(a)^3*im(a))/2401, (a <= 25/7)∧(a > 1)), (nan, True))
Rapid solution [src]
         //             ___________                 ___   __________    \     //             ___________                 ___   __________    \
         ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |     ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |
         ||- -- - - - -------------  for -- + - + ------------------ > 0|     ||- -- - - - -------------  for -- + - + ------------------ > 0|
x1 = I*im|<  49   7         49           49   7           49            | + re|<  49   7         49           49   7           49            |
         ||                                                             |     ||                                                             |
         ||          nan                          otherwise             |     ||          nan                          otherwise             |
         \\                                                             /     \\                                                             /
$$x_{1} = \operatorname{re}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
         //             ___________                 ___   __________    \     //             ___________                 ___   __________    \
         ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |     ||  1    a   \/ 50 + 14*a       1    a   \/ 2 *\/ 25 + 7*a     |
         ||- -- - - + -------------  for -- + - - ------------------ > 0|     ||- -- - - + -------------  for -- + - - ------------------ > 0|
x2 = I*im|<  49   7         49           49   7           49            | + re|<  49   7         49           49   7           49            |
         ||                                                             |     ||                                                             |
         ||          nan                          otherwise             |     ||          nan                          otherwise             |
         \\                                                             /     \\                                                             /
$$x_{2} = \operatorname{re}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
         //         ___________                     ___   __________     \     //         ___________                     ___   __________     \
         ||  1    \/ 50 - 14*a    a      1    a   \/ 2 *\/ 25 - 7*a      |     ||  1    \/ 50 - 14*a    a      1    a   \/ 2 *\/ 25 - 7*a      |
         ||- -- - ------------- + -  for -- - - + ------------------ <= 0|     ||- -- - ------------- + -  for -- - - + ------------------ <= 0|
x3 = I*im|<  49         49        7      49   7           49             | + re|<  49         49        7      49   7           49             |
         ||                                                              |     ||                                                              |
         ||          nan                          otherwise              |     ||          nan                          otherwise              |
         \\                                                              /     \\                                                              /
$$x_{3} = \operatorname{re}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
         //             ___________                   ___   __________     \     //             ___________                   ___   __________     \
         ||  1    a   \/ 50 - 14*a         1    a   \/ 2 *\/ 25 - 7*a      |     ||  1    a   \/ 50 - 14*a         1    a   \/ 2 *\/ 25 - 7*a      |
         ||- -- + - + -------------  for - -- + - + ------------------ >= 0|     ||- -- + - + -------------  for - -- + - + ------------------ >= 0|
x4 = I*im|<  49   7         49             49   7           49             | + re|<  49   7         49             49   7           49             |
         ||                                                                |     ||                                                                |
         ||          nan                           otherwise               |     ||          nan                           otherwise               |
         \\                                                                /     \\                                                                /
$$x_{4} = \operatorname{re}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
x4 = re(Piecewise((a/7 + sqrt(50 - 14*a/49 - 1/49, a/7 + sqrt(2)*sqrt(25 - 7*a)/49 - 1/49 >= 0), (nan, True))) + i*im(Piecewise((a/7 + sqrt(50 - 14*a)/49 - 1/49, a/7 + sqrt(2)*sqrt(25 - 7*a)/49 - 1/49 >= 0), (nan, True))))