Question

Помогите плиззз очень срочно дам 50 б​

Answer 1

1.

$\sqrt{27y} + \sqrt{75y} - \sqrt{48y} = \\ \\ \sqrt{9 \times 3} + \sqrt{25 \times 3} - \sqrt{16 \times 3} = \\ \\ 3 \sqrt{3} + 5 \sqrt{3} - 4\sqrt{3} = 4 \sqrt{3}$

2.

$- 4 \sqrt{5} = - \sqrt{ {4}^{2} \times 5} = - \sqrt{16 \times 5} = - \sqrt{80} \\ \\ - 42 = - \sqrt{ {42}^{2} } = - \sqrt{1764} \\ \\ - 2\sqrt{7} = - \sqrt{ {2}^{2} \times 7 } = - \sqrt{4 \times 7} = - \sqrt{28} \\ \\1) - \sqrt{1764} \: \: \:2) - \sqrt{80} \: \: \: 3)- \sqrt{28}$

3.

$(3 \sqrt{7} - 2 \sqrt{3} ) \times \sqrt{7} + \sqrt{84} = \\ (3 \sqrt{7} \times \sqrt{7} - 2 \sqrt{3} \times \sqrt{7} ) + \sqrt{84} = \\ ( 3 \times 7 - 2 \sqrt{21} ) + \sqrt{84} = \\ 21 - 2 \sqrt{21} + 84 = \\ 21 - 2 \sqrt{21} + \sqrt{4 \times 21} = \\ 21 - 2 \sqrt{21} + 2 \sqrt{21} = 21$

4.

$\frac{3 - {b}^{2} }{ \sqrt{3} + b} = \frac{( \sqrt{3} - b)( \sqrt{3} + b)}{ \sqrt{3} + b } = \sqrt{3} - b$