9x^2-4x-18=0

Solution for 9x^2-4x-18=0 equation:

9x^2-4x-18=0

a = 9; b = -4; c = -18;
Δ = b2-4ac
Δ = -42-4·9·(-18)
Δ = 664
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:

$\sqrt{\Delta}=\sqrt{664}=\sqrt{4*166}=\sqrt{4}*\sqrt{166}=2\sqrt{166}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-2\sqrt{166}}{2*9}=\frac{4-2\sqrt{166}}{18}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+2\sqrt{166}}{2*9}=\frac{4+2\sqrt{166}}{18}
$