210=x^2-x

Solution for 210=x^2-x equation:

210=x^2-x

We move all terms to the left:

210-(x^2-x)=0

We get rid of parentheses

-x^2+x+210=0

We add all the numbers together, and all the variables

-1x^2+x+210=0

a = -1; b = 1; c = +210;
Δ = b2-4ac
Δ = 12-4·(-1)·210
Δ = 841
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{841}=29$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-29}{2*-1}=\frac{-30}{-2}
=+15
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+29}{2*-1}=\frac{28}{-2}
=-14
$