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

Solution for 9=(x+5)(x-3) equation:

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

We move all terms to the left:

9-((x+5)(x-3))=0

We multiply parentheses ..

-((+x^2-3x+5x-15))+9=0


We calculate terms in parentheses: -((+x^2-3x+5x-15)), so:

(+x^2-3x+5x-15)

We get rid of parentheses

x^2-3x+5x-15

We add all the numbers together, and all the variables

x^2+2x-15

Back to the equation:

-(x^2+2x-15)


We get rid of parentheses

-x^2-2x+15+9=0

We add all the numbers together, and all the variables

-1x^2-2x+24=0

a = -1; b = -2; c = +24;
Δ = b2-4ac
Δ = -22-4·(-1)·24
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-10}{2*-1}=\frac{-8}{-2}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+10}{2*-1}=\frac{12}{-2}
=-6
$