(x+7)(x-7)=120

Solution for (x+7)(x-7)=120 equation:

(x+7)(x-7)=120

We move all terms to the left:

(x+7)(x-7)-(120)=0

We use the square of the difference formula

x^2-49-120=0

We add all the numbers together, and all the variables

x^2-169=0

a = 1; b = 0; c = -169;
Δ = b2-4ac
Δ = 02-4·1·(-169)
Δ = 676
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{676}=26$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-26}{2*1}=\frac{-26}{2}
=-13
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+26}{2*1}=\frac{26}{2}
=13
$