.(6x+7)+(13x+21)=180

Solution for .(6x+7)+(13x+21)=180 equation:

.(6x+7)+(13x+21)=180

We move all terms to the left:

.(6x+7)+(13x+21)-(180)=0

We multiply parentheses

6x^2+(13x+21)-180+=0

We get rid of parentheses

6x^2+13x+21-180+=0

We add all the numbers together, and all the variables

6x^2+13x=0

a = 6; b = 13; c = 0;
Δ = b2-4ac
Δ = 132-4·6·0
Δ = 169
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{169}=13$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(13)-13}{2*6}=\frac{-26}{12}
=-2+1/6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(13)+13}{2*6}=\frac{0}{12}
=0
$