$\sqrt{289}=17;-\sqrt{144}=-12;\sqrt{\frac{81}{225}}=\frac{9}{15}=\frac{3}{5};\sqrt{(-3)^{2}}=3;\sqrt{a^{2}}=\left | a\right |$
$\sqrt{289}=17;-\sqrt{144}=-12;\sqrt{\frac{81}{225}}=\frac{9}{15}=\frac{3}{5};\sqrt{(-3)^{2}}=3;\sqrt{a^{2}}=\left | a\right |$