5x^2-10x-55=0

Solution for 5x^2-10x-55=0 equation:

5x^2-10x-55=0

a = 5; b = -10; c = -55;
Δ = b2-4ac
Δ = -102-4·5·(-55)
Δ = 1200
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:

$\sqrt{\Delta}=\sqrt{1200}=\sqrt{400*3}=\sqrt{400}*\sqrt{3}=20\sqrt{3}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-20\sqrt{3}}{2*5}=\frac{10-20\sqrt{3}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+20\sqrt{3}}{2*5}=\frac{10+20\sqrt{3}}{10}
$