8x(x-18)=90

Solution for 8x(x-18)=90 equation:

8x(x-18)=90

We move all terms to the left:

8x(x-18)-(90)=0

We multiply parentheses

8x^2-144x-90=0

a = 8; b = -144; c = -90;
Δ = b2-4ac
Δ = -1442-4·8·(-90)
Δ = 23616
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:

$\sqrt{\Delta}=\sqrt{23616}=\sqrt{576*41}=\sqrt{576}*\sqrt{41}=24\sqrt{41}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-144)-24\sqrt{41}}{2*8}=\frac{144-24\sqrt{41}}{16}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-144)+24\sqrt{41}}{2*8}=\frac{144+24\sqrt{41}}{16}
$