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

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

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

We multiply parentheses ..

(+36x^2+36x-16x-16)=0

We get rid of parentheses

36x^2+36x-16x-16=0

We add all the numbers together, and all the variables

36x^2+20x-16=0

a = 36; b = 20; c = -16;
Δ = b2-4ac
Δ = 202-4·36·(-16)
Δ = 2704
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2704}=52$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-52}{2*36}=\frac{-72}{72}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+52}{2*36}=\frac{32}{72}
=4/9
$