-5(4-x)x=-5x+20

Solution for -5(4-x)x=-5x+20 equation:

-5(4-x)x=-5x+20

We move all terms to the left:

-5(4-x)x-(-5x+20)=0

We add all the numbers together, and all the variables

-5(-1x+4)x-(-5x+20)=0

We multiply parentheses

5x^2-20x-(-5x+20)=0

We get rid of parentheses

5x^2-20x+5x-20=0

We add all the numbers together, and all the variables

5x^2-15x-20=0

a = 5; b = -15; c = -20;
Δ = b2-4ac
Δ = -152-4·5·(-20)
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-25}{2*5}=\frac{-10}{10}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+25}{2*5}=\frac{40}{10}
=4
$