x(2x+4)=168

Solution for x(2x+4)=168 equation:

x(2x+4)=168

We move all terms to the left:

x(2x+4)-(168)=0

We multiply parentheses

2x^2+4x-168=0

a = 2; b = 4; c = -168;
Δ = b2-4ac
Δ = 42-4·2·(-168)
Δ = 1360
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:

$\sqrt{\Delta}=\sqrt{1360}=\sqrt{16*85}=\sqrt{16}*\sqrt{85}=4\sqrt{85}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-4\sqrt{85}}{2*2}=\frac{-4-4\sqrt{85}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+4\sqrt{85}}{2*2}=\frac{-4+4\sqrt{85}}{4}
$