(2x+9)(2x-8)=0

Solution for (2x+9)(2x-8)=0 equation:

(2x+9)(2x-8)=0

We multiply parentheses ..

(+4x^2-16x+18x-72)=0

We get rid of parentheses

4x^2-16x+18x-72=0

We add all the numbers together, and all the variables

4x^2+2x-72=0

a = 4; b = 2; c = -72;
Δ = b2-4ac
Δ = 22-4·4·(-72)
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-34}{2*4}=\frac{-36}{8}
=-4+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+34}{2*4}=\frac{32}{8}
=4
$