(4x+20)(x-10)=0

Solution for (4x+20)(x-10)=0 equation:

(4x+20)(x-10)=0

We multiply parentheses ..

(+4x^2-40x+20x-200)=0

We get rid of parentheses

4x^2-40x+20x-200=0

We add all the numbers together, and all the variables

4x^2-20x-200=0

a = 4; b = -20; c = -200;
Δ = b2-4ac
Δ = -202-4·4·(-200)
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*4}=\frac{-40}{8}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+60}{2*4}=\frac{80}{8}
=10
$