0=x^2-9x-28

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

0=x^2-9x-28

We move all terms to the left:

0-(x^2-9x-28)=0

We add all the numbers together, and all the variables

-(x^2-9x-28)=0

We get rid of parentheses

-x^2+9x+28=0

We add all the numbers together, and all the variables

-1x^2+9x+28=0

a = -1; b = 9; c = +28;
Δ = b2-4ac
Δ = 92-4·(-1)·28
Δ = 193
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-\sqrt{193}}{2*-1}=\frac{-9-\sqrt{193}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+\sqrt{193}}{2*-1}=\frac{-9+\sqrt{193}}{-2}
$