Answer
The solutions are $\sqrt{5} $ and $-\sqrt{5}.$
Work Step by Step
$ 7r^{2}-10=25\qquad$ ...add $10$ to each side.
$ 7r^{2}-10+10=25+10\qquad$ ...simplify.
$ 7r^{2}=35\qquad$ ...divide each side with $7$
$ r^{2}=5\qquad$ ...take square roots of each side.
$\sqrt{r^{2}}=\sqrt{5}\qquad$ ...simplify.
...When solving an equation of the form $x^{2}=s$ where $s>0$,
we find both the positive and negative solutions.
$r=\pm\sqrt{5}$
