7x^2+18x-8=0

Solution for 7x^2+18x-8=0 equation:

7x^2+18x-8=0

a = 7; b = 18; c = -8;
Δ = b2-4ac
Δ = 182-4·7·(-8)
Δ = 548
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:

$\sqrt{\Delta}=\sqrt{548}=\sqrt{4*137}=\sqrt{4}*\sqrt{137}=2\sqrt{137}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(18)-2\sqrt{137}}{2*7}=\frac{-18-2\sqrt{137}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(18)+2\sqrt{137}}{2*7}=\frac{-18+2\sqrt{137}}{14}
$