2x^2-8x-78=0

Solution for 2x^2-8x-78=0 equation:

2x^2-8x-78=0

a = 2; b = -8; c = -78;
Δ = b2-4ac
Δ = -82-4·2·(-78)
Δ = 688
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:

$\sqrt{\Delta}=\sqrt{688}=\sqrt{16*43}=\sqrt{16}*\sqrt{43}=4\sqrt{43}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-4\sqrt{43}}{2*2}=\frac{8-4\sqrt{43}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+4\sqrt{43}}{2*2}=\frac{8+4\sqrt{43}}{4}
$