Question

Solve. x^2 – x = 20.

Answer 1

By completing squares:
\[x^2 – x = 20\]
\[(x–\frac{1}{2})^2 = 20 + \frac{1}{4}\]
\[x-\frac{1}{2} = \pm \sqrt{(\frac{81}{4})} = \pm \frac{9}{2}\]
\[x=\frac{1}{2} \pm \frac{9}{2} = 5\ or -4\]