[tex] \bf a) \: \sqrt{81} + \sqrt{64} = \\ \\ = \bf \sqrt{ {9}^{2} } + \sqrt{ {8}^{2} } = \\ \\ \bf = 9 + 8 = \red{ 17} [/tex]
[tex] \space [/tex]
[tex] \bf b) \: \sqrt{20} + \sqrt{45 } + \sqrt{5} = \\ \\ \bf = 2 \sqrt{5} + 3 \sqrt{5} + 1\sqrt{5} = \\ \\ \bf = \blue{6 \sqrt{5} } [/tex]
[tex] \space [/tex]
[tex] \bf c) \: \sqrt{ {6}^{2} + {8}^{2} } - \sqrt{ {3}^{4} } = \\ \\ \bf = \sqrt{36 + 64} - {3}^{2} = \\ \\ \bf = \sqrt{100} - 9 = \\ \\ \bf = 10 - 9 = \orange{1} [/tex]
