Given the equation:
$$\left(\frac{1}{\left(x - 4\right)^{2}} - \frac{7}{x - 4}\right) + 10 = 0$$
Multiply the equation sides by the denominators:
(-4 + x)^2
we get:
$$\left(x - 4\right)^{2} \left(\left(\frac{1}{\left(x - 4\right)^{2}} - \frac{7}{x - 4}\right) + 10\right) = 0$$
$$10 x^{2} - 87 x + 189 = 0$$
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
$$a = 10$$
$$b = -87$$
$$c = 189$$
, then
D = b^2 - 4 * a * c =
(-87)^2 - 4 * (10) * (189) = 9
Because D > 0, then the equation has two roots.
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
or
$$x_{1} = \frac{9}{2}$$
$$x_{2} = \frac{21}{5}$$