Question

5√20+3√45−2√80−4√125

Answer 1

$5 \sqrt{20} + 3 \sqrt{45} - 2 \sqrt{80} - 4 \sqrt{125} = 5 \sqrt{4 \times 5} + 3 \sqrt{9 \times 5} - 2 \sqrt{16 \times 5} - 4 \sqrt{25 \times 5} = \\ \\ = 5 \times 2 \sqrt{5} + 3 \times 3 \sqrt{5} - 2 \times 4 \sqrt{5} - 4 \times 5 \sqrt{5} = 10 \sqrt{5} + 9 \sqrt{5} - 8 \sqrt{5} - 20 \sqrt{5} = - 9 \sqrt{5}$