4x(x+2)=56

Solution for 4x(x+2)=56 equation:

4x(x+2)=56

We move all terms to the left:

4x(x+2)-(56)=0

We multiply parentheses

4x^2+8x-56=0

a = 4; b = 8; c = -56;
Δ = b2-4ac
Δ = 82-4·4·(-56)
Δ = 960
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:

$\sqrt{\Delta}=\sqrt{960}=\sqrt{64*15}=\sqrt{64}*\sqrt{15}=8\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-8\sqrt{15}}{2*4}=\frac{-8-8\sqrt{15}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+8\sqrt{15}}{2*4}=\frac{-8+8\sqrt{15}}{8}
$