7x^2-76x-28=0

Solution for 7x^2-76x-28=0 equation:

7x^2-76x-28=0

a = 7; b = -76; c = -28;
Δ = b2-4ac
Δ = -762-4·7·(-28)
Δ = 6560
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:

$\sqrt{\Delta}=\sqrt{6560}=\sqrt{16*410}=\sqrt{16}*\sqrt{410}=4\sqrt{410}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-76)-4\sqrt{410}}{2*7}=\frac{76-4\sqrt{410}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-76)+4\sqrt{410}}{2*7}=\frac{76+4\sqrt{410}}{14}
$