Question

.......7a e b passo a passo.......

Answer 1

$a) ( \sqrt{2} - \sqrt{6} ).( \sqrt{2} +2 \sqrt{6} ) = \sqrt{2} .\sqrt{2} + 2 \sqrt{6}.\sqrt{2} - \sqrt{6}.\sqrt{2}- 2\sqrt{6}. \sqrt{6} \\ \\ 2 + 2 \sqrt{6}.\sqrt{2} - \sqrt{6}.\sqrt{2}-12 \\ \\ -4 + 2 \sqrt{12} - \sqrt{12} \\ \\ -10+ \sqrt{12} \\ \\ -10 + \sqrt{2^{2}.3} \\ \\ -10 + 2 \sqrt{3} \\ \\ -10 + 2.1,7 = -10 + 3,4 = -0,6 \\ \\ b) (5 - \sqrt{7} )(5 + \sqrt{7} ) \\ \\ 5^{2}-( \sqrt{7} )^{2} \\ \\ 25-7 = 18$

Espero ter ajudado.