8x^2-7=121

Solution for 8x^2-7=121 equation:

8x^2-7=121

We move all terms to the left:

8x^2-7-(121)=0

We add all the numbers together, and all the variables

8x^2-128=0

a = 8; b = 0; c = -128;
Δ = b2-4ac
Δ = 02-4·8·(-128)
Δ = 4096
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4096}=64$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-64}{2*8}=\frac{-64}{16}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+64}{2*8}=\frac{64}{16}
=4
$