3(x+2)(x+5)=0

Solution for 3(x+2)(x+5)=0 equation:

3(x+2)(x+5)=0

We multiply parentheses ..

3(+x^2+5x+2x+10)=0

We multiply parentheses

3x^2+15x+6x+30=0

We add all the numbers together, and all the variables

3x^2+21x+30=0

a = 3; b = 21; c = +30;
Δ = b2-4ac
Δ = 212-4·3·30
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-9}{2*3}=\frac{-30}{6}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+9}{2*3}=\frac{-12}{6}
=-2
$