(5x-5)(8x+4)=0

Solution for (5x-5)(8x+4)=0 equation:

(5x-5)(8x+4)=0

We multiply parentheses ..

(+40x^2+20x-40x-20)=0

We get rid of parentheses

40x^2+20x-40x-20=0

We add all the numbers together, and all the variables

40x^2-20x-20=0

a = 40; b = -20; c = -20;
Δ = b2-4ac
Δ = -202-4·40·(-20)
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-60}{2*40}=\frac{-40}{80}
=-1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+60}{2*40}=\frac{80}{80}
=1
$