Question

пж помогите по алгебре

Answer 1

$\sqrt{5} - \sqrt{20} = \sqrt{5} - \sqrt{4 \times 5} = \sqrt{5} - 2 \times \sqrt{5} = - \sqrt{5}$
$\sqrt{15} \times \sqrt{6} \div \sqrt{10} = \sqrt{15 \times 6 \div 10} = \sqrt{9} = 3$
$ab \sqrt{2} = \sqrt{ {a}^{2} \times {b}^{2} \times 2}$