(3x+6)*(5x+2)=255

Solution for (3x+6)*(5x+2)=255 equation:

(3x+6)(5x+2)=255

We move all terms to the left:

(3x+6)(5x+2)-(255)=0

We multiply parentheses ..

(+15x^2+6x+30x+12)-255=0

We get rid of parentheses

15x^2+6x+30x+12-255=0

We add all the numbers together, and all the variables

15x^2+36x-243=0

a = 15; b = 36; c = -243;
Δ = b2-4ac
Δ = 362-4·15·(-243)
Δ = 15876
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{15876}=126$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(36)-126}{2*15}=\frac{-162}{30}
=-5+2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(36)+126}{2*15}=\frac{90}{30}
=3
$