171=x2-28x

Solution for 171=x2-28x equation:

171=x2-28x

We move all terms to the left:

171-(x2-28x)=0

We add all the numbers together, and all the variables

-(+x^2-28x)+171=0

We get rid of parentheses

-x^2+28x+171=0

We add all the numbers together, and all the variables

-1x^2+28x+171=0

a = -1; b = 28; c = +171;
Δ = b2-4ac
Δ = 282-4·(-1)·171
Δ = 1468
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:

$\sqrt{\Delta}=\sqrt{1468}=\sqrt{4*367}=\sqrt{4}*\sqrt{367}=2\sqrt{367}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-2\sqrt{367}}{2*-1}=\frac{-28-2\sqrt{367}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+2\sqrt{367}}{2*-1}=\frac{-28+2\sqrt{367}}{-2}
$