(5x-15)(4x-2)=0

Solution for (5x-15)(4x-2)=0 equation:

(5x-15)(4x-2)=0

We multiply parentheses ..

(+20x^2-10x-60x+30)=0

We get rid of parentheses

20x^2-10x-60x+30=0

We add all the numbers together, and all the variables

20x^2-70x+30=0

a = 20; b = -70; c = +30;
Δ = b2-4ac
Δ = -702-4·20·30
Δ = 2500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2500}=50$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-70)-50}{2*20}=\frac{20}{40}
=1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-70)+50}{2*20}=\frac{120}{40}
=3
$