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x^2-1=1+(1/2)*y equation

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Numerical solution:

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The solution

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 2           y
x  - 1 = 1 + -
             2
$$x^{2} - 1 = \frac{y}{2} + 1$$
Detail solution
Move right part of the equation to
left part with negative sign.

The equation is transformed from
$$x^{2} - 1 = \frac{y}{2} + 1$$
to
$$\left(x^{2} - 1\right) + \left(- \frac{y}{2} - 1\right) = 0$$
This equation is of the form
a*x^2 + b*x + c = 0

A quadratic equation can be solved
using the discriminant.
The roots of the quadratic equation:
$$x_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$x_{2} = \frac{- \sqrt{D} - b}{2 a}$$
where D = b^2 - 4*a*c - it is the discriminant.
Because
$$a = 1$$
$$b = 0$$
$$c = - \frac{y}{2} - 2$$
, then
D = b^2 - 4 * a * c = 

(0)^2 - 4 * (1) * (-2 - y/2) = 8 + 2*y

The equation has two roots.
x1 = (-b + sqrt(D)) / (2*a)

x2 = (-b - sqrt(D)) / (2*a)

or
$$x_{1} = \frac{\sqrt{2 y + 8}}{2}$$
$$x_{2} = - \frac{\sqrt{2 y + 8}}{2}$$
Vieta's Theorem
it is reduced quadratic equation
$$p x + q + x^{2} = 0$$
where
$$p = \frac{b}{a}$$
$$p = 0$$
$$q = \frac{c}{a}$$
$$q = - \frac{y}{2} - 2$$
Vieta Formulas
$$x_{1} + x_{2} = - p$$
$$x_{1} x_{2} = q$$
$$x_{1} + x_{2} = 0$$
$$x_{1} x_{2} = - \frac{y}{2} - 2$$
The graph
Rapid solution [src]
          ___________________________                                         ___________________________                                 
       4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\     4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\
       \/  (8 + 2*re(y))  + 4*im (y) *cos|---------------------------|   I*\/  (8 + 2*re(y))  + 4*im (y) *sin|---------------------------|
                                         \             2             /                                       \             2             /
x1 = - --------------------------------------------------------------- - -----------------------------------------------------------------
                                      2                                                                  2                                
$$x_{1} = - \frac{i \sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2} - \frac{\sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2}$$
        ___________________________                                         ___________________________                                 
     4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\     4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\
     \/  (8 + 2*re(y))  + 4*im (y) *cos|---------------------------|   I*\/  (8 + 2*re(y))  + 4*im (y) *sin|---------------------------|
                                       \             2             /                                       \             2             /
x2 = --------------------------------------------------------------- + -----------------------------------------------------------------
                                    2                                                                  2                                
$$x_{2} = \frac{i \sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2} + \frac{\sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2}$$
x2 = i*((2*re(y) + 8)^2 + 4*im(y)^2)^(1/4)*sin(atan2(2*im(y, 2*re(y) + 8)/2)/2 + ((2*re(y) + 8)^2 + 4*im(y)^2)^(1/4)*cos(atan2(2*im(y), 2*re(y) + 8)/2)/2)
Sum and product of roots [src]
sum
     ___________________________                                         ___________________________                                       ___________________________                                         ___________________________                                 
  4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\     4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\   4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\     4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\
  \/  (8 + 2*re(y))  + 4*im (y) *cos|---------------------------|   I*\/  (8 + 2*re(y))  + 4*im (y) *sin|---------------------------|   \/  (8 + 2*re(y))  + 4*im (y) *cos|---------------------------|   I*\/  (8 + 2*re(y))  + 4*im (y) *sin|---------------------------|
                                    \             2             /                                       \             2             /                                     \             2             /                                       \             2             /
- --------------------------------------------------------------- - ----------------------------------------------------------------- + --------------------------------------------------------------- + -----------------------------------------------------------------
                                 2                                                                  2                                                                  2                                                                  2                                
$$\left(- \frac{i \sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2} - \frac{\sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2}\right) + \left(\frac{i \sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2} + \frac{\sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2}\right)$$
=
0
$$0$$
product
/     ___________________________                                         ___________________________                                 \ /   ___________________________                                         ___________________________                                 \
|  4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\     4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\| |4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\     4 /              2       2        /atan2(2*im(y), 8 + 2*re(y))\|
|  \/  (8 + 2*re(y))  + 4*im (y) *cos|---------------------------|   I*\/  (8 + 2*re(y))  + 4*im (y) *sin|---------------------------|| |\/  (8 + 2*re(y))  + 4*im (y) *cos|---------------------------|   I*\/  (8 + 2*re(y))  + 4*im (y) *sin|---------------------------||
|                                    \             2             /                                       \             2             /| |                                  \             2             /                                       \             2             /|
|- --------------------------------------------------------------- - -----------------------------------------------------------------|*|--------------------------------------------------------------- + -----------------------------------------------------------------|
\                                 2                                                                  2                                / \                               2                                                                  2                                /
$$\left(- \frac{i \sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2} - \frac{\sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2}\right) \left(\frac{i \sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2} + \frac{\sqrt[4]{\left(2 \operatorname{re}{\left(y\right)} + 8\right)^{2} + 4 \left(\operatorname{im}{\left(y\right)}\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}{2} \right)}}{2}\right)$$
=
    _______________________                                
   /            2     2      I*atan2(2*im(y), 8 + 2*re(y)) 
-\/  (4 + re(y))  + im (y) *e                              
-----------------------------------------------------------
                             2                             
$$- \frac{\sqrt{\left(\operatorname{re}{\left(y\right)} + 4\right)^{2} + \left(\operatorname{im}{\left(y\right)}\right)^{2}} e^{i \operatorname{atan_{2}}{\left(2 \operatorname{im}{\left(y\right)},2 \operatorname{re}{\left(y\right)} + 8 \right)}}}{2}$$
-sqrt((4 + re(y))^2 + im(y)^2)*exp(i*atan2(2*im(y), 8 + 2*re(y)))/2