x^2-90x=3600

Solution for x^2-90x=3600 equation:

x^2-90x=3600

We move all terms to the left:

x^2-90x-(3600)=0

a = 1; b = -90; c = -3600;
Δ = b2-4ac
Δ = -902-4·1·(-3600)
Δ = 22500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{22500}=150$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-90)-150}{2*1}=\frac{-60}{2}
=-30
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-90)+150}{2*1}=\frac{240}{2}
=120
$