(m+7)(m+8)=0

Solution for (m+7)(m+8)=0 equation:

(m+7)(m+8)=0

We multiply parentheses ..

(+m^2+8m+7m+56)=0

We get rid of parentheses

m^2+8m+7m+56=0

We add all the numbers together, and all the variables

m^2+15m+56=0

a = 1; b = 15; c = +56;
Δ = b2-4ac
Δ = 152-4·1·56
Δ = 1
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1}=1$
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-1}{2*1}=\frac{-16}{2}
=-8
$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+1}{2*1}=\frac{-14}{2}
=-7
$