Solve $5x^2+4x-2=0$ in simplest surd form.

$D=16+40=56$, so $x=\frac{-4\pm \sqrt{56}}{10}=\frac{-4\pm 2\sqrt{14}}{10}=\frac{-2\pm \sqrt{14}}{5}$. Cancelling the 2 from the numerator but not from the denominator leaves $\frac{-2\pm \sqrt{14}}{10}$; dividing by $a=5$ instead of $2a=10$ doubles both roots.