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

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

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

10x^2+50x+60=0

a = 10; b = 50; c = +60;
Δ = b2-4ac
Δ = 502-4·10·60
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(50)-10}{2*10}=\frac{-60}{20}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(50)+10}{2*10}=\frac{-40}{20}
=-2
$