(2x+10)(2x-10)=69

Solution for (2x+10)(2x-10)=69 equation:

(2x+10)(2x-10)=69

We move all terms to the left:

(2x+10)(2x-10)-(69)=0

We use the square of the difference formula

4x^2-100-69=0

We add all the numbers together, and all the variables

4x^2-169=0

a = 4; b = 0; c = -169;
Δ = b2-4ac
Δ = 02-4·4·(-169)
Δ = 2704
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2704}=52$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-52}{2*4}=\frac{-52}{8}
=-6+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+52}{2*4}=\frac{52}{8}
=6+1/2
$