X(4x-85)=90

Solution for X(4x-85)=90 equation:

X(4X-85)=90

We move all terms to the left:

X(4X-85)-(90)=0

We multiply parentheses

4X^2-85X-90=0

a = 4; b = -85; c = -90;
Δ = b2-4ac
Δ = -852-4·4·(-90)
Δ = 8665
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{-(-85)-\sqrt{8665}}{2*4}=\frac{85-\sqrt{8665}}{8}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-85)+\sqrt{8665}}{2*4}=\frac{85+\sqrt{8665}}{8}
$