-x^2-10x=-36

Solution for -x^2-10x=-36 equation:

-x^2-10x=-36

We move all terms to the left:

-x^2-10x-(-36)=0

We add all the numbers together, and all the variables

-1x^2-10x+36=0

a = -1; b = -10; c = +36;
Δ = b2-4ac
Δ = -102-4·(-1)·36
Δ = 244
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{244}=\sqrt{4*61}=\sqrt{4}*\sqrt{61}=2\sqrt{61}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-2\sqrt{61}}{2*-1}=\frac{10-2\sqrt{61}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+2\sqrt{61}}{2*-1}=\frac{10+2\sqrt{61}}{-2}
$