18=3(x+4);x

Solution for 18=3(x+4);x equation:

18=3(x+4)x

We move all terms to the left:

18-(3(x+4)x)=0


We calculate terms in parentheses: -(3(x+4)x), so:

3(x+4)x

We multiply parentheses

3x^2+12x

Back to the equation:

-(3x^2+12x)


We get rid of parentheses

-3x^2-12x+18=0

a = -3; b = -12; c = +18;
Δ = b2-4ac
Δ = -122-4·(-3)·18
Δ = 360
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:

$\sqrt{\Delta}=\sqrt{360}=\sqrt{36*10}=\sqrt{36}*\sqrt{10}=6\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-6\sqrt{10}}{2*-3}=\frac{12-6\sqrt{10}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+6\sqrt{10}}{2*-3}=\frac{12+6\sqrt{10}}{-6}
$