[tex]x = 10 \: \: \: \: \: y = - 6 \\ \sqrt{ {x}^{2} - {y}^{2} } = \sqrt{ {10}^{2} - ( - 6) {}^{2} } = \sqrt{100 - 36} = \sqrt{64} = \\= \sqrt{ {8}^{2} } = 8[/tex]