0=x^2-30x-15

Solution for 0=x^2-30x-15 equation:

0=x^2-30x-15

We move all terms to the left:

0-(x^2-30x-15)=0

We add all the numbers together, and all the variables

-(x^2-30x-15)=0

We get rid of parentheses

-x^2+30x+15=0

We add all the numbers together, and all the variables

-1x^2+30x+15=0

a = -1; b = 30; c = +15;
Δ = b2-4ac
Δ = 302-4·(-1)·15
Δ = 960
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{960}=\sqrt{64*15}=\sqrt{64}*\sqrt{15}=8\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-8\sqrt{15}}{2*-1}=\frac{-30-8\sqrt{15}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+8\sqrt{15}}{2*-1}=\frac{-30+8\sqrt{15}}{-2}
$