81x^2+4x-36=0

Solution for 81x^2+4x-36=0 equation:

81x^2+4x-36=0

a = 81; b = 4; c = -36;
Δ = b2-4ac
Δ = 42-4·81·(-36)
Δ = 11680
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:

$\sqrt{\Delta}=\sqrt{11680}=\sqrt{16*730}=\sqrt{16}*\sqrt{730}=4\sqrt{730}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-4\sqrt{730}}{2*81}=\frac{-4-4\sqrt{730}}{162}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+4\sqrt{730}}{2*81}=\frac{-4+4\sqrt{730}}{162}
$