(2x+6)(2x+8)=168

Solution for (2x+6)(2x+8)=168 equation:

(2x+6)(2x+8)=168

We move all terms to the left:

(2x+6)(2x+8)-(168)=0

We multiply parentheses ..

(+4x^2+16x+12x+48)-168=0

We get rid of parentheses

4x^2+16x+12x+48-168=0

We add all the numbers together, and all the variables

4x^2+28x-120=0

a = 4; b = 28; c = -120;
Δ = b2-4ac
Δ = 282-4·4·(-120)
Δ = 2704
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2704}=52$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-52}{2*4}=\frac{-80}{8}
=-10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+52}{2*4}=\frac{24}{8}
=3
$