(4x+8)(x+5)=0

Solution for (4x+8)(x+5)=0 equation:

(4x+8)(x+5)=0

We multiply parentheses ..

(+4x^2+20x+8x+40)=0

We get rid of parentheses

4x^2+20x+8x+40=0

We add all the numbers together, and all the variables

4x^2+28x+40=0

a = 4; b = 28; c = +40;
Δ = b2-4ac
Δ = 282-4·4·40
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-12}{2*4}=\frac{-40}{8}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+12}{2*4}=\frac{-16}{8}
=-2
$