135=(X+6)*(x)

Solution for 135=(X+6)*(x) equation:

135=(X+6)(X)

We move all terms to the left:

135-((X+6)(X))=0


We calculate terms in parentheses: -((X+6)X), so:

(X+6)X

We multiply parentheses

X^2+6X

Back to the equation:

-(X^2+6X)


We get rid of parentheses

-X^2-6X+135=0

We add all the numbers together, and all the variables

-1X^2-6X+135=0

a = -1; b = -6; c = +135;
Δ = b2-4ac
Δ = -62-4·(-1)·135
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-24}{2*-1}=\frac{-18}{-2}
=+9
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+24}{2*-1}=\frac{30}{-2}
=-15
$