(X+8)(x+4)=320

Solution for (X+8)(x+4)=320 equation:

(X+8)(X+4)=320

We move all terms to the left:

(X+8)(X+4)-(320)=0

We multiply parentheses ..

(+X^2+4X+8X+32)-320=0

We get rid of parentheses

X^2+4X+8X+32-320=0

We add all the numbers together, and all the variables

X^2+12X-288=0

a = 1; b = 12; c = -288;
Δ = b2-4ac
Δ = 122-4·1·(-288)
Δ = 1296
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1296}=36$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-36}{2*1}=\frac{-48}{2}
=-24
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+36}{2*1}=\frac{24}{2}
=12
$