(3x+)(x+13)=180

Solution for (3x+)(x+13)=180 equation:

(3x+)(x+13)=180

We move all terms to the left:

(3x+)(x+13)-(180)=0

We add all the numbers together, and all the variables

(+3x)(x+13)-180=0

We multiply parentheses ..

(+3x^2+39x)-180=0

We get rid of parentheses

3x^2+39x-180=0

a = 3; b = 39; c = -180;
Δ = b2-4ac
Δ = 392-4·3·(-180)
Δ = 3681
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:

$\sqrt{\Delta}=\sqrt{3681}=\sqrt{9*409}=\sqrt{9}*\sqrt{409}=3\sqrt{409}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(39)-3\sqrt{409}}{2*3}=\frac{-39-3\sqrt{409}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(39)+3\sqrt{409}}{2*3}=\frac{-39+3\sqrt{409}}{6}
$