3(x^2-13x+6)=18

Solution for 3(x^2-13x+6)=18 equation:

3(x^2-13x+6)=18

We move all terms to the left:

3(x^2-13x+6)-(18)=0

We multiply parentheses

3x^2-39x+18-18=0

We add all the numbers together, and all the variables

3x^2-39x=0

a = 3; b = -39; c = 0;
Δ = b2-4ac
Δ = -392-4·3·0
Δ = 1521
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1521}=39$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-39)-39}{2*3}=\frac{0}{6}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-39)+39}{2*3}=\frac{78}{6}
=13
$