0=13x^2-84x+36

Solution for 0=13x^2-84x+36 equation:

0=13x^2-84x+36

We move all terms to the left:

0-(13x^2-84x+36)=0

We add all the numbers together, and all the variables

-(13x^2-84x+36)=0

We get rid of parentheses

-13x^2+84x-36=0

a = -13; b = 84; c = -36;
Δ = b2-4ac
Δ = 842-4·(-13)·(-36)
Δ = 5184
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5184}=72$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(84)-72}{2*-13}=\frac{-156}{-26}
=+6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(84)+72}{2*-13}=\frac{-12}{-26}
=6/13
$