-4b(2b+6)=-4b

Solution for -4b(2b+6)=-4b equation:

-4b(2b+6)=-4b

We move all terms to the left:

-4b(2b+6)-(-4b)=0

We multiply parentheses

-8b^2-24b-(-4b)=0

We get rid of parentheses

-8b^2-24b+4b=0

We add all the numbers together, and all the variables

-8b^2-20b=0

a = -8; b = -20; c = 0;
Δ = b2-4ac
Δ = -202-4·(-8)·0
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-20}{2*-8}=\frac{0}{-16}
=0
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+20}{2*-8}=\frac{40}{-16}
=-2+1/2
$