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

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

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

18x^2-18x-36=0

a = 18; b = -18; c = -36;
Δ = b2-4ac
Δ = -182-4·18·(-36)
Δ = 2916
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2916}=54$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18)-54}{2*18}=\frac{-36}{36}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18)+54}{2*18}=\frac{72}{36}
=2
$