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Решите задачу:

$1.7 - 4 \sqrt{7} + 4 - ( \sqrt{7} - 3)( \sqrt{7} + 3) + 4 \sqrt{7} \\ 7 + 4 - (7 - 9) \\ 7 + 4 - ( - 2) \\ 7 + 4 + 2 = 13 \\ \frac{6}{ \sqrt{3} } = \frac{6 \sqrt{3} }{ \sqrt{3} \sqrt{3} } = \frac{6 \sqrt{3} }{3} = 2 \sqrt{3} \\ 2. \sqrt{2} x = 2 \sqrt{2} - 3 \sqrt{2} \\ \sqrt{2} x = - \sqrt{2} \\ x = - 1 \\ 3.5 \sqrt{3} = \sqrt{5 {}^{2} \times 3} = \sqrt{25 \times 3} = \sqrt{75} \\ - 2 \sqrt{13} = \sqrt{ - 2 {}^{2} \times 13} = \sqrt{4 \times 13} = \sqrt{52}$