-9x^2-9x+28=0

Solution for -9x^2-9x+28=0 equation:

-9x^2-9x+28=0

a = -9; b = -9; c = +28;
Δ = b2-4ac
Δ = -92-4·(-9)·28
Δ = 1089
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1089}=33$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-33}{2*-9}=\frac{-24}{-18}
=1+1/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+33}{2*-9}=\frac{42}{-18}
=-2+1/3
$