(x+3)(x-3)=80

Solution for (x+3)(x-3)=80 equation:

(x+3)(x-3)=80

We move all terms to the left:

(x+3)(x-3)-(80)=0

We use the square of the difference formula

x^2-9-80=0

We add all the numbers together, and all the variables

x^2-89=0

a = 1; b = 0; c = -89;
Δ = b2-4ac
Δ = 02-4·1·(-89)
Δ = 356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{356}=\sqrt{4*89}=\sqrt{4}*\sqrt{89}=2\sqrt{89}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{89}}{2*1}=\frac{0-2\sqrt{89}}{2}
=-\frac{2\sqrt{89}}{2}
=-\sqrt{89}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{89}}{2*1}=\frac{0+2\sqrt{89}}{2}
=\frac{2\sqrt{89}}{2}
=\sqrt{89}
$