(3x)(x+2)=105

Solution for (3x)(x+2)=105 equation:

(3x)(x+2)=105

We move all terms to the left:

(3x)(x+2)-(105)=0

We multiply parentheses

3x^2+6x-105=0

a = 3; b = 6; c = -105;
Δ = b2-4ac
Δ = 62-4·3·(-105)
Δ = 1296
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1296}=36$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-36}{2*3}=\frac{-42}{6}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+36}{2*3}=\frac{30}{6}
=5
$