\(\left(a-b\right)\cdot\sqrt{3}=\sqrt{\left(a-b\right)^2\cdot3}\)

\(-\left(a-b\right)\cdot\sqrt{\dfrac{2}{a-b}}=-\sqrt{\left(a-b\right)^2\cdot\dfrac{2}{a-b}}=-\sqrt{2a-2b}\)

\(\left(a-3\right)\cdot\sqrt{\dfrac{1}{a-3}}=\sqrt{\dfrac{\left(a-3\right)^2}{a-3}}=\sqrt{a-3}\)

D, b nhân căn bậc 5 phần ab với a<0, b<0

a: \(13\sqrt{11}=\sqrt{13^2\cdot11}=\sqrt{1859}\)

b: \(-8\sqrt{2}=-\sqrt{64\cdot2}=-\sqrt{128}\)

c: \(a\sqrt{5a}=\sqrt{a^2\cdot5a}=\sqrt{5a^3}\)

d: \(b\sqrt{\dfrac{5}{ab}}=-\sqrt{b^2\cdot\dfrac{5}{ab}}=-\sqrt{\dfrac{5b}{a}}\)

ab4√a = √((ab4)2 a)= √(a2 b^8 a)= √(a3b8 )

a: \(xy^2\sqrt{x}=\sqrt{x^2y^4\cdot x}=\sqrt{x^3y^4}\)

b: \(\dfrac{2}{x}\sqrt{\dfrac{15xy}{4}}=-\sqrt{\dfrac{4}{x^2}\cdot\dfrac{15xy}{4}}=-\sqrt{\dfrac{15y}{x}}\)

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

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

b)  x - 29 x  với x < 0

= - - 29 x 2 x = - - 29 x