4x+4x(x-7)=20

Solution for 4x+4x(x-7)=20 equation:

4x+4x(x-7)=20

We move all terms to the left:

4x+4x(x-7)-(20)=0

We multiply parentheses

4x^2+4x-28x-20=0

We add all the numbers together, and all the variables

4x^2-24x-20=0

a = 4; b = -24; c = -20;
Δ = b2-4ac
Δ = -242-4·4·(-20)
Δ = 896
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{896}=\sqrt{64*14}=\sqrt{64}*\sqrt{14}=8\sqrt{14}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-24)-8\sqrt{14}}{2*4}=\frac{24-8\sqrt{14}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-24)+8\sqrt{14}}{2*4}=\frac{24+8\sqrt{14}}{8}
$