(x+4)(x+6)=15

Solution for (x+4)(x+6)=15 equation:

(x+4)(x+6)=15

We move all terms to the left:

(x+4)(x+6)-(15)=0

We multiply parentheses ..

(+x^2+6x+4x+24)-15=0

We get rid of parentheses

x^2+6x+4x+24-15=0

We add all the numbers together, and all the variables

x^2+10x+9=0

a = 1; b = 10; c = +9;
Δ = b2-4ac
Δ = 102-4·1·9
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{-(10)-8}{2*1}=\frac{-18}{2}
=-9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+8}{2*1}=\frac{-2}{2}
=-1
$