(2x+8)(9x-4)=0

Solution for (2x+8)(9x-4)=0 equation:

(2x+8)(9x-4)=0

We multiply parentheses ..

(+18x^2-8x+72x-32)=0

We get rid of parentheses

18x^2-8x+72x-32=0

We add all the numbers together, and all the variables

18x^2+64x-32=0

a = 18; b = 64; c = -32;
Δ = b2-4ac
Δ = 642-4·18·(-32)
Δ = 6400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6400}=80$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(64)-80}{2*18}=\frac{-144}{36}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(64)+80}{2*18}=\frac{16}{36}
=4/9
$