3x^2-90x-18=0

Solution for 3x^2-90x-18=0 equation:

3x^2-90x-18=0

a = 3; b = -90; c = -18;
Δ = b2-4ac
Δ = -902-4·3·(-18)
Δ = 8316
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:

$\sqrt{\Delta}=\sqrt{8316}=\sqrt{36*231}=\sqrt{36}*\sqrt{231}=6\sqrt{231}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-90)-6\sqrt{231}}{2*3}=\frac{90-6\sqrt{231}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-90)+6\sqrt{231}}{2*3}=\frac{90+6\sqrt{231}}{6}
$