3*x*x+x-990=0

Solution for 3*x*x+x-990=0 equation:

3x*x+x-990=0

We add all the numbers together, and all the variables

x+3x*x-990=0

Wy multiply elements

3x^2+x-990=0

a = 3; b = 1; c = -990;
Δ = b2-4ac
Δ = 12-4·3·(-990)
Δ = 11881
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{11881}=109$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-109}{2*3}=\frac{-110}{6}
=-18+1/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+109}{2*3}=\frac{108}{6}
=18
$