-4x^2=-40x

Solution for -4x^2=-40x equation:

-4x^2=-40x

We move all terms to the left:

-4x^2-(-40x)=0

We get rid of parentheses

-4x^2+40x=0

a = -4; b = 40; c = 0;
Δ = b2-4ac
Δ = 402-4·(-4)·0
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-40}{2*-4}=\frac{-80}{-8}
=+10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+40}{2*-4}=\frac{0}{-8}
=0
$