x(3x+3)=168

Solution for x(3x+3)=168 equation:

x(3x+3)=168

We move all terms to the left:

x(3x+3)-(168)=0

We multiply parentheses

3x^2+3x-168=0

a = 3; b = 3; c = -168;
Δ = b2-4ac
Δ = 32-4·3·(-168)
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-45}{2*3}=\frac{-48}{6}
=-8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+45}{2*3}=\frac{42}{6}
=7
$