\(\sqrt{1} = 1\)

\(\sqrt{9} = 3\)

\(\sqrt{121} = 11\)

\(\sqrt{4} + \sqrt{25} = 2 + 5 = 7\)

\(8 \sqrt{121} - 5 \sqrt{4} = 8 ⋅ 11 - 5 ⋅ 2 = 78\)

\(\sqrt{4} ⋅ \sqrt{16} = 2 ⋅ 4 = 8\)

\((-9 \sqrt{8})^{2} = (-9)^{2} ⋅ \sqrt{8}^{2} = 81 ⋅ 8 = 648 \text{.}\)

\((7 \sqrt{8} - 9) (7 \sqrt{8} + 9) = (7 \sqrt{8})^{2} - 9^{2} = 49 ⋅ 8 - 81 = 392 - 81 = 311 \text{.}\)

\((\sqrt{11})^{2} = 11 \text{.}\)

\(-4 (\sqrt{7})^{2} = -4 ⋅ 7 = -28 \text{.}\)

\(5 \sqrt{3} + 4 \sqrt{3} = 9 \sqrt{3}\)

\(6 \sqrt{5} ⋅ 4 \sqrt{7} = 24 \sqrt{35}\)

\({\sqrt{80} \over \sqrt{8}} = \sqrt{10}\)

\({21 \sqrt{4} \over 3 \sqrt{2}} = {21 \over 3} ⋅ {\sqrt{4} \over \sqrt{2}} = 7 \sqrt{2}\)

\({30 \sqrt{18} \over 6 \sqrt{2}} = {30 \over 6} ⋅ {\sqrt{18} \over \sqrt{2}} = 5 ⋅ \sqrt{9} = 5 ⋅ 3 = 15\)