9x^2-12x-36=0.

Solution for 9x^2-12x-36=0. equation:

9x^2-12x-36=0.

a = 9; b = -12; c = -36;
Δ = b2-4ac
Δ = -122-4·9·(-36)
Δ = 1440
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:

$\sqrt{\Delta}=\sqrt{1440}=\sqrt{144*10}=\sqrt{144}*\sqrt{10}=12\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-12\sqrt{10}}{2*9}=\frac{12-12\sqrt{10}}{18}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+12\sqrt{10}}{2*9}=\frac{12+12\sqrt{10}}{18}
$