-3x^2+12x+351=0

Solution for -3x^2+12x+351=0 equation:

-3x^2+12x+351=0

a = -3; b = 12; c = +351;
Δ = b2-4ac
Δ = 122-4·(-3)·351
Δ = 4356
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4356}=66$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-66}{2*-3}=\frac{-78}{-6}
=+13
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+66}{2*-3}=\frac{54}{-6}
=-9
$