X^2=80x+81

Solution for X^2=80x+81 equation:

X^2=80X+81

We move all terms to the left:

X^2-(80X+81)=0

We get rid of parentheses

X^2-80X-81=0

a = 1; b = -80; c = -81;
Δ = b2-4ac
Δ = -802-4·1·(-81)
Δ = 6724
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6724}=82$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-80)-82}{2*1}=\frac{-2}{2}
=-1
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-80)+82}{2*1}=\frac{162}{2}
=81
$