0=x^2-28x+30

Solution for 0=x^2-28x+30 equation:

0=x^2-28x+30

We move all terms to the left:

0-(x^2-28x+30)=0

We add all the numbers together, and all the variables

-(x^2-28x+30)=0

We get rid of parentheses

-x^2+28x-30=0

We add all the numbers together, and all the variables

-1x^2+28x-30=0

a = -1; b = 28; c = -30;
Δ = b2-4ac
Δ = 282-4·(-1)·(-30)
Δ = 664
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:

$\sqrt{\Delta}=\sqrt{664}=\sqrt{4*166}=\sqrt{4}*\sqrt{166}=2\sqrt{166}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-2\sqrt{166}}{2*-1}=\frac{-28-2\sqrt{166}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+2\sqrt{166}}{2*-1}=\frac{-28+2\sqrt{166}}{-2}
$