\(=3ab^2\)

\(\sqrt{3^2a^2b^4}\)=3a\(b^2\)

48 y 4 = 16 . 3 y 4 = 4 . y 2 3

1: \(3\sqrt8-5\sqrt{18}\)

\(=3\cdot2\sqrt2-5\cdot3\sqrt2\)

\(=6\sqrt2-15\sqrt2=-9\sqrt2\)

2:

\(7\sqrt3=\sqrt{7^2\cdot3}=\sqrt{147}\)

mà 147>141

nên \(7\sqrt3>\sqrt{141}\)

3: \(\sqrt{\frac{5}{27}}=\sqrt{\frac{5}{9\cdot3}}=\sqrt{\frac{15}{81}}=\frac{\sqrt{15}}{9}\)

\(\sqrt{\frac{11}{64}}=\frac{\sqrt{11}}{\sqrt{64}}=\frac{\sqrt{11}}{8}\)

8 y 2 = 4 . 2 y 2 = 2 y 2 = - 2 y 2 ( với y < 0 )

√(28a4b2 ) = √((2a2b)2.7) = √7 |2a2b| = 2√7a2b (do b ≥ 0)