(X+2)(x+4)=15

Solution for (X+2)(x+4)=15 equation:

(X+2)(X+4)=15

We move all terms to the left:

(X+2)(X+4)-(15)=0

We multiply parentheses ..

(+X^2+4X+2X+8)-15=0

We get rid of parentheses

X^2+4X+2X+8-15=0

We add all the numbers together, and all the variables

X^2+6X-7=0

a = 1; b = 6; c = -7;
Δ = b2-4ac
Δ = 62-4·1·(-7)
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-8}{2*1}=\frac{-14}{2}
=-7
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+8}{2*1}=\frac{2}{2}
=1
$