Question

$(7\sqrt{2}-\sqrt{19} ) * (\sqrt{19} +7\sqrt{2})$

Answer 1

$(7 \sqrt{2} - \sqrt{19} ) \times ( \sqrt{19} + 7 \sqrt{2}) = (7 \sqrt{2} - \sqrt{19} \times (7 \sqrt{2} + \sqrt{19} ) = 49 \times 2 - 19 = 98 - 19 = 79$