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

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

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

We move all terms to the left:

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


We calculate terms in parentheses: -(4x+4x(x-7)), so:

4x+4x(x-7)

We multiply parentheses

4x^2+4x-28x

We add all the numbers together, and all the variables

4x^2-24x

Back to the equation:

-(4x^2-24x)


We get rid of parentheses

-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}
$