5x^2-10x-77=0

Solution for 5x^2-10x-77=0 equation:

5x^2-10x-77=0

a = 5; b = -10; c = -77;
Δ = b2-4ac
Δ = -102-4·5·(-77)
Δ = 1640
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:

$\sqrt{\Delta}=\sqrt{1640}=\sqrt{4*410}=\sqrt{4}*\sqrt{410}=2\sqrt{410}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-2\sqrt{410}}{2*5}=\frac{10-2\sqrt{410}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+2\sqrt{410}}{2*5}=\frac{10+2\sqrt{410}}{10}
$