0=8x^2-5x-90

Solution for 0=8x^2-5x-90 equation:

0=8x^2-5x-90

We move all terms to the left:

0-(8x^2-5x-90)=0

We add all the numbers together, and all the variables

-(8x^2-5x-90)=0

We get rid of parentheses

-8x^2+5x+90=0

a = -8; b = 5; c = +90;
Δ = b2-4ac
Δ = 52-4·(-8)·90
Δ = 2905
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{-(5)-\sqrt{2905}}{2*-8}=\frac{-5-\sqrt{2905}}{-16}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+\sqrt{2905}}{2*-8}=\frac{-5+\sqrt{2905}}{-16}
$