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

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

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

20x^2-10x-10=0

a = 20; b = -10; c = -10;
Δ = b2-4ac
Δ = -102-4·20·(-10)
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-30}{2*20}=\frac{-20}{40}
=-1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+30}{2*20}=\frac{40}{40}
=1
$