-2x2-x+28=0

Solution for -2x2-x+28=0 equation:

-2x^2-x+28=0

We add all the numbers together, and all the variables

-2x^2-1x+28=0

a = -2; b = -1; c = +28;
Δ = b2-4ac
Δ = -12-4·(-2)·28
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1)-15}{2*-2}=\frac{-14}{-4}
=3+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+15}{2*-2}=\frac{16}{-4}
=-4
$