x^2+36x-81=0

Solution for x^2+36x-81=0 equation:

x^2+36x-81=0

a = 1; b = 36; c = -81;
Δ = b2-4ac
Δ = 362-4·1·(-81)
Δ = 1620
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:

$\sqrt{\Delta}=\sqrt{1620}=\sqrt{324*5}=\sqrt{324}*\sqrt{5}=18\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(36)-18\sqrt{5}}{2*1}=\frac{-36-18\sqrt{5}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(36)+18\sqrt{5}}{2*1}=\frac{-36+18\sqrt{5}}{2}
$