-21x^2+27x+30=0

Solution for -21x^2+27x+30=0 equation:

-21x^2+27x+30=0

a = -21; b = 27; c = +30;
Δ = b2-4ac
Δ = 272-4·(-21)·30
Δ = 3249
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3249}=57$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(27)-57}{2*-21}=\frac{-84}{-42}
=+2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(27)+57}{2*-21}=\frac{30}{-42}
=-5/7
$