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

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

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

We move all terms to the left:

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

We add all the numbers together, and all the variables

(x+5)(-1x+5)-9=0

We multiply parentheses ..

(-1x^2+5x-5x+25)-9=0

We get rid of parentheses

-1x^2+5x-5x+25-9=0

We add all the numbers together, and all the variables

-1x^2+16=0

a = -1; b = 0; c = +16;
Δ = b2-4ac
Δ = 02-4·(-1)·16
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{-(0)-8}{2*-1}=\frac{-8}{-2}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+8}{2*-1}=\frac{8}{-2}
=-4
$