X^2-17x=90

Solution for X^2-17x=90 equation:

X^2-17X=90

We move all terms to the left:

X^2-17X-(90)=0

a = 1; b = -17; c = -90;
Δ = b2-4ac
Δ = -172-4·1·(-90)
Δ = 649
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-17)-\sqrt{649}}{2*1}=\frac{17-\sqrt{649}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-17)+\sqrt{649}}{2*1}=\frac{17+\sqrt{649}}{2}
$