-3a^2-21a-18=0

Solution for -3a^2-21a-18=0 equation:

-3a^2-21a-18=0

a = -3; b = -21; c = -18;
Δ = b2-4ac
Δ = -212-4·(-3)·(-18)
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-15}{2*-3}=\frac{6}{-6}
=-1
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+15}{2*-3}=\frac{36}{-6}
=-6
$