Question

$a) \: (4 \sqrt{5) {}^{2} }-0.2( - \sqrt{900} ){}^{2}$
$b) ( \sqrt{5} + 1) {}^{2} - 2 \sqrt{5}$

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Answer 1

$a) (4\sqrt{5})^{2} - 0.2(-\sqrt{900})^{2} = 4^{2} * \sqrt{5}^{2} - 0.2 * \sqrt{900}^{2} = 16 * 5 - 0.2 * 900 = 80 - 180 = -100;\\ b) (\sqrt{5} + 1)^{2} - 2\sqrt{5} = \sqrt{5}^{2} + 2*1*\sqrt{5} + 1^{2} - 2\sqrt{5} = 5 + 2\sqrt{5} + 1 -2\sqrt{5} = 6.$