-x^2-72x+36=0

Solution for -x^2-72x+36=0 equation:

-x^2-72x+36=0

We add all the numbers together, and all the variables

-1x^2-72x+36=0

a = -1; b = -72; c = +36;
Δ = b2-4ac
Δ = -722-4·(-1)·36
Δ = 5328
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:

$\sqrt{\Delta}=\sqrt{5328}=\sqrt{144*37}=\sqrt{144}*\sqrt{37}=12\sqrt{37}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-72)-12\sqrt{37}}{2*-1}=\frac{72-12\sqrt{37}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-72)+12\sqrt{37}}{2*-1}=\frac{72+12\sqrt{37}}{-2}
$