x^2+72x+81=0

Solution for x^2+72x+81=0 equation:

x^2+72x+81=0

a = 1; b = 72; c = +81;
Δ = b2-4ac
Δ = 722-4·1·81
Δ = 4860
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:

$\sqrt{\Delta}=\sqrt{4860}=\sqrt{324*15}=\sqrt{324}*\sqrt{15}=18\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(72)-18\sqrt{15}}{2*1}=\frac{-72-18\sqrt{15}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(72)+18\sqrt{15}}{2*1}=\frac{-72+18\sqrt{15}}{2}
$