f*(x)=-2*x-5 equation
The teacher will be very surprised to see your correct solution 😉
The solution
Detail solution
Given the linear equation:
f*(x) = -2*x-5
Expand brackets in the left part
fx = -2*x-5
Move the summands with the unknown x
from the right part to the left part:
$$f x + 2 x = -5$$
Divide both parts of the equation by (2*x + f*x)/x
x = -5 / ((2*x + f*x)/x)
We get the answer: x = -5/(2 + f)
The solution of the parametric equation
Given the equation with a parameter:
$$f x = - 2 x - 5$$
Коэффициент при x равен
$$f + 2$$
then possible cases for f :
$$f < -2$$
$$f = -2$$
Consider all cases in more detail:
With
$$f < -2$$
the equation
$$5 - x = 0$$
its solution
$$x = 5$$
With
$$f = -2$$
the equation
$$5 = 0$$
its solution
no solutions
5*(2 + re(f)) 5*I*im(f)
x1 = - --------------------- + ---------------------
2 2 2 2
(2 + re(f)) + im (f) (2 + re(f)) + im (f)
$$x_{1} = - \frac{5 \left(\operatorname{re}{\left(f\right)} + 2\right)}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}} + \frac{5 i \operatorname{im}{\left(f\right)}}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}}$$
x1 = -5*(re(f) + 2)/((re(f) + 2)^2 + im(f)^2) + 5*i*im(f)/((re(f) + 2)^2 + im(f)^2)
Sum and product of roots
[src]
5*(2 + re(f)) 5*I*im(f)
- --------------------- + ---------------------
2 2 2 2
(2 + re(f)) + im (f) (2 + re(f)) + im (f)
$$- \frac{5 \left(\operatorname{re}{\left(f\right)} + 2\right)}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}} + \frac{5 i \operatorname{im}{\left(f\right)}}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}}$$
5*(2 + re(f)) 5*I*im(f)
- --------------------- + ---------------------
2 2 2 2
(2 + re(f)) + im (f) (2 + re(f)) + im (f)
$$- \frac{5 \left(\operatorname{re}{\left(f\right)} + 2\right)}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}} + \frac{5 i \operatorname{im}{\left(f\right)}}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}}$$
5*(2 + re(f)) 5*I*im(f)
- --------------------- + ---------------------
2 2 2 2
(2 + re(f)) + im (f) (2 + re(f)) + im (f)
$$- \frac{5 \left(\operatorname{re}{\left(f\right)} + 2\right)}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}} + \frac{5 i \operatorname{im}{\left(f\right)}}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}}$$
5*(-2 - re(f) + I*im(f))
------------------------
2 2
(2 + re(f)) + im (f)
$$\frac{5 \left(- \operatorname{re}{\left(f\right)} + i \operatorname{im}{\left(f\right)} - 2\right)}{\left(\operatorname{re}{\left(f\right)} + 2\right)^{2} + \left(\operatorname{im}{\left(f\right)}\right)^{2}}$$
5*(-2 - re(f) + i*im(f))/((2 + re(f))^2 + im(f)^2)