0=s2-13s-30

Solution for 0=s2-13s-30 equation:

0=s2-13s-30

We move all terms to the left:

0-(s2-13s-30)=0

We add all the numbers together, and all the variables

-(+s^2-13s-30)+0=0

We add all the numbers together, and all the variables

-(+s^2-13s-30)=0

We get rid of parentheses

-s^2+13s+30=0

We add all the numbers together, and all the variables

-1s^2+13s+30=0

a = -1; b = 13; c = +30;
Δ = b2-4ac
Δ = 132-4·(-1)·30
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(13)-17}{2*-1}=\frac{-30}{-2}
=+15
$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(13)+17}{2*-1}=\frac{4}{-2}
=-2
$