(m+8)(m+9)=16

Solution for (m+8)(m+9)=16 equation:

(m+8)(m+9)=16

We move all terms to the left:

(m+8)(m+9)-(16)=0

We multiply parentheses ..

(+m^2+9m+8m+72)-16=0

We get rid of parentheses

m^2+9m+8m+72-16=0

We add all the numbers together, and all the variables

m^2+17m+56=0

a = 1; b = 17; c = +56;
Δ = b2-4ac
Δ = 172-4·1·56
Δ = 65
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$m_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(17)-\sqrt{65}}{2*1}=\frac{-17-\sqrt{65}}{2}
$
$m_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(17)+\sqrt{65}}{2*1}=\frac{-17+\sqrt{65}}{2}
$