-3x^2-8x+18=0

Solution for -3x^2-8x+18=0 equation:

-3x^2-8x+18=0

a = -3; b = -8; c = +18;
Δ = b2-4ac
Δ = -82-4·(-3)·18
Δ = 280
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:

$\sqrt{\Delta}=\sqrt{280}=\sqrt{4*70}=\sqrt{4}*\sqrt{70}=2\sqrt{70}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-2\sqrt{70}}{2*-3}=\frac{8-2\sqrt{70}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+2\sqrt{70}}{2*-3}=\frac{8+2\sqrt{70}}{-6}
$