(3x-15)(x+17)=0

Solution for (3x-15)(x+17)=0 equation:

(3x-15)(x+17)=0

We multiply parentheses ..

(+3x^2+51x-15x-255)=0

We get rid of parentheses

3x^2+51x-15x-255=0

We add all the numbers together, and all the variables

3x^2+36x-255=0

a = 3; b = 36; c = -255;
Δ = b2-4ac
Δ = 362-4·3·(-255)
Δ = 4356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4356}=66$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(36)-66}{2*3}=\frac{-102}{6}
=-17
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(36)+66}{2*3}=\frac{30}{6}
=5
$