(2a+4)(a+5)=0

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

(2a+4)(a+5)=0

We multiply parentheses ..

(+2a^2+10a+4a+20)=0

We get rid of parentheses

2a^2+10a+4a+20=0

We add all the numbers together, and all the variables

2a^2+14a+20=0

a = 2; b = 14; c = +20;
Δ = b2-4ac
Δ = 142-4·2·20
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-6}{2*2}=\frac{-20}{4}
=-5
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+6}{2*2}=\frac{-8}{4}
=-2
$