(9x+5)(2x-4)=0

Solution for (9x+5)(2x-4)=0 equation:

(9x+5)(2x-4)=0

We multiply parentheses ..

(+18x^2-36x+10x-20)=0

We get rid of parentheses

18x^2-36x+10x-20=0

We add all the numbers together, and all the variables

18x^2-26x-20=0

a = 18; b = -26; c = -20;
Δ = b2-4ac
Δ = -262-4·18·(-20)
Δ = 2116
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2116}=46$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-26)-46}{2*18}=\frac{-20}{36}
=-5/9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-26)+46}{2*18}=\frac{72}{36}
=2
$