2x2+10x-66=0

Solution for 2x2+10x-66=0 equation:

2x^2+10x-66=0

a = 2; b = 10; c = -66;
Δ = b2-4ac
Δ = 102-4·2·(-66)
Δ = 628
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:

$\sqrt{\Delta}=\sqrt{628}=\sqrt{4*157}=\sqrt{4}*\sqrt{157}=2\sqrt{157}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-2\sqrt{157}}{2*2}=\frac{-10-2\sqrt{157}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+2\sqrt{157}}{2*2}=\frac{-10+2\sqrt{157}}{4}
$