(5x-15)(-x+2)=0

Solution for (5x-15)(-x+2)=0 equation:

(5x-15)(-x+2)=0

We add all the numbers together, and all the variables

(5x-15)(-1x+2)=0

We multiply parentheses ..

(-5x^2+10x+15x-30)=0

We get rid of parentheses

-5x^2+10x+15x-30=0

We add all the numbers together, and all the variables

-5x^2+25x-30=0

a = -5; b = 25; c = -30;
Δ = b2-4ac
Δ = 252-4·(-5)·(-30)
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(25)-5}{2*-5}=\frac{-30}{-10}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(25)+5}{2*-5}=\frac{-20}{-10}
=+2
$