7*x*x-8x-64=0

Solution for 7*x*x-8x-64=0 equation:

7x*x-8x-64=0

We add all the numbers together, and all the variables

-8x+7x*x-64=0

Wy multiply elements

7x^2-8x-64=0

a = 7; b = -8; c = -64;
Δ = b2-4ac
Δ = -82-4·7·(-64)
Δ = 1856
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:

$\sqrt{\Delta}=\sqrt{1856}=\sqrt{64*29}=\sqrt{64}*\sqrt{29}=8\sqrt{29}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-8\sqrt{29}}{2*7}=\frac{8-8\sqrt{29}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+8\sqrt{29}}{2*7}=\frac{8+8\sqrt{29}}{14}
$