Given the equation:
$$\left(\frac{1}{\left(x - 1\right)^{2}} + \frac{4}{x - 1}\right) - 12 = 0$$
Multiply the equation sides by the denominators:
(-1 + x)^2
we get:
$$\left(x - 1\right)^{2} \left(\left(\frac{1}{\left(x - 1\right)^{2}} + \frac{4}{x - 1}\right) - 12\right) = 0$$
$$- 12 x^{2} + 28 x - 15 = 0$$
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
$$a = -12$$
$$b = 28$$
$$c = -15$$
, then
D = b^2 - 4 * a * c =
(28)^2 - 4 * (-12) * (-15) = 64
Because D > 0, then the equation has two roots.
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
or
$$x_{1} = \frac{5}{6}$$
$$x_{2} = \frac{3}{2}$$