(x+7)*(2x+8)=0

Solution for (x+7)*(2x+8)=0 equation:

(x+7)(2x+8)=0

We multiply parentheses ..

(+2x^2+8x+14x+56)=0

We get rid of parentheses

2x^2+8x+14x+56=0

We add all the numbers together, and all the variables

2x^2+22x+56=0

a = 2; b = 22; c = +56;
Δ = b2-4ac
Δ = 222-4·2·56
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(22)-6}{2*2}=\frac{-28}{4}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(22)+6}{2*2}=\frac{-16}{4}
=-4
$