(x+5)(x-3)=-15

Solution for (x+5)(x-3)=-15 equation:

(X+5)(X-3)=-15

We move all terms to the left:

(X+5)(X-3)-(-15)=0

We add all the numbers together, and all the variables

(X+5)(X-3)+15=0

We multiply parentheses ..

(+X^2-3X+5X-15)+15=0

We get rid of parentheses

X^2-3X+5X-15+15=0

We add all the numbers together, and all the variables

X^2+2X=0

a = 1; b = 2; c = 0;
Δ = b2-4ac
Δ = 22-4·1·0
Δ = 4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4}=2$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-2}{2*1}=\frac{-4}{2}
=-2
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+2}{2*1}=\frac{0}{2}
=0
$