\(\sqrt{64ab^3}-3\sqrt{12a^3b^3}+2ab\sqrt{9ab}-5b\sqrt{81a^3b}\\ =\sqrt{64b^2.ab}-3\sqrt{4a^2b^2.ab}+2ab.3\sqrt{ab}-5b\sqrt{81a^2.ab}\\ =\left|8b\right|\sqrt{ab}+3\left|2ab\right|\sqrt{3ab}+6ab\sqrt{ab}-5b\left|9a\right|\sqrt{ab}\\ =8b\sqrt{ab}-6ab\sqrt{3ab}-39ab\sqrt{ab}\\ \)

a) Ta có: \(5\sqrt{a}-3\sqrt{25a^3}+2\sqrt{36ab^2}-2\sqrt{9a}\)

\(=5\sqrt{a}-15a\sqrt{a}+12b\sqrt{a}-6\sqrt{a}\)

\(=-\sqrt{a}-15a\sqrt{a}+12\sqrt{a}b\)

b) Ta có: \(\sqrt{64ab^3}-3\sqrt{12a^3b^3}+2ab\sqrt{9ab}-5b\sqrt{81a^3b}\)

\(=8b\sqrt{a}-6ab\sqrt{3ab}+6ab\sqrt{ab}-45a^2b\sqrt{ab}\)

a)\(5\sqrt{a}-3\sqrt{25a^3}+2\sqrt{36ab^2}-2\sqrt{9a}=5\sqrt{a}-15\left|a\right|\sqrt{a}+12\left|b\right|\sqrt{a}-6\sqrt{a}=-\sqrt{a}-15a\sqrt{a}+12b\sqrt{a}\)

b)\(\sqrt{64ab^3}-3\sqrt{12a^3b^3}+2ab\sqrt{9ab}-5b\sqrt{81a^3b}\)

\(=8\left|b\right|\sqrt{ab}-6\left|ab\right|\sqrt{3ab}+6ab\sqrt{ab}-45b\left|a\right|\sqrt{ab}\)

\(=8b\sqrt{ab}-6ab\sqrt{3ab}+6ab\sqrt{ab}-45ab\sqrt{ab}\)

\(=8b\sqrt{ab}-6ab\sqrt{3ab}-39ab\sqrt{ab}\)

a) \(a-\sqrt{a}\)

b) \(-5ab\sqrt{ab}\)

a) Ta có:

\(5\sqrt{a}-4b\sqrt{25a^3}+5a\sqrt{16ab^2}-2\sqrt{9a}\)

\(=5\sqrt{a}-4b.5a\sqrt{a}+5a.4b\sqrt{a}-2.3\sqrt{a}\)

\(=5\sqrt{a}-20ab\sqrt{a}+20ab\sqrt{a}-6\sqrt{a}\) \(=-\sqrt{a}\)

b) Ta có:

\(5a\sqrt{64ab^3}-\sqrt{3}.\sqrt{12a^3b^3}+2ab\sqrt{9ab}\) \(-5b\sqrt{81a^3b}\)

\(=5a.8b\sqrt{ab}-\sqrt{3.12a^3b^3}+2ab.3\sqrt{ab}\) \(-5b.9a\sqrt{ab}\)

\(=40ab\sqrt{ab}-6ab\sqrt{ab}+6ab\sqrt{ab}-45ab\)\(\sqrt{ab}\)

\(=-5ab\sqrt{ab}\)

a)5\(\sqrt{a}\)\(-4b\sqrt{25a^3}+5a\sqrt{16ab^2}-2\sqrt{9a}\)

=5\(\sqrt{a}-20ab\sqrt{a}+20ab\sqrt{a}-6\sqrt{a}\)

= \(\sqrt{a}\left(5-20ab+20ab-6\right)\)

= -\(\sqrt{a}\)

Bạn làm đc bài này chưa chỉ mình với

a: \(=6\sqrt{a}+\dfrac{1}{3}\sqrt{a}-3\sqrt{a}+\sqrt{7}=\dfrac{10}{3}\sqrt{a}+\sqrt{7}\)

b: \(=5a\cdot5b\sqrt{ab}+\sqrt{3}\cdot2\sqrt{3}\cdot ab\sqrt{ab}+9ab\cdot3\sqrt{ab}-5b\cdot9a\sqrt{ab}\)

\(=25ab\sqrt{ab}+12ab\sqrt{ab}+27ab\sqrt{ab}-45ab\sqrt{ab}\)

\(=19ab\sqrt{ab}\)

c: \(=\dfrac{\sqrt{ab}}{b}+\sqrt{ab}-\dfrac{a}{b}\cdot\dfrac{\sqrt{b}}{\sqrt{a}}\)

\(=\sqrt{ab}\left(\dfrac{1}{b}+1\right)-\dfrac{\sqrt{a}}{\sqrt{b}}\)

\(=\sqrt{ab}\)

d: \(=11\sqrt{5a}-5\sqrt{5a}+2\sqrt{5a}-12\sqrt{5a}+9\sqrt{a}\)

\(=-4\sqrt{5a}+9\sqrt{a}\)

Ta có: \(5a\sqrt{64ab^3}-\sqrt{3}.\sqrt{12a^3b^3}-5b\sqrt{81a^3b}\)

    \(=5a.8b.\sqrt{ab}-\sqrt{3}.2\sqrt{3}.ab.\sqrt{ab}-5b.9a\sqrt{ab}\)

    \(=40ab.\sqrt{ab}-6ab.\sqrt{ab}-45ab.\sqrt{ab}\)

    \(=40ab.\sqrt{ab}-6ab.\sqrt{ab}-45ab.\sqrt{ab}\)

    \(=-11ab\sqrt{ab}\)

\(5a\sqrt{64ab^3}\) \(-\sqrt{3}\)\(.\sqrt{12a^3b^3}\)\(-5b\sqrt{81a^3b}\)

\(=40ab\sqrt{ab}\)\(-6ab\sqrt{ab}-45ab\sqrt{ab}\)

\(=\left(40ab-6ab-45ab\right)\sqrt{ab}\)

\(=-11ab\sqrt{ab}\)

\(=5a\sqrt{64b^2\left(ab\right)}-\sqrt{3\cdot12a^2b^2\left(ab\right)}-5b\sqrt{81a^2\left(ab\right)}\) 

\(=5a\cdot8b\sqrt{ab}-\sqrt{36a^2b^2\left(ab\right)}-5b\cdot9a\sqrt{ab}\) 

\(=40ab\sqrt{ab}-6ab\sqrt{ab}-45ab\sqrt{ab}\)        

\(=-11ab\sqrt{ab}\)            

a) Ta có: \(\sqrt{125}-4\sqrt{45}+3\sqrt{20}-\sqrt{80}\)

         \(=5\sqrt{5}-4.3\sqrt{5}+3.2\sqrt{5}-4\sqrt{5}\)

         \(=5\sqrt{5}-12\sqrt{5}+6\sqrt{5}-4\sqrt{5}\)

         \(=-5\sqrt{5}\)

         \(\approx-11,18033989\)

b, \(5\sqrt{a}-4b\sqrt{25a^2}+5a\sqrt{16ab^2}-2\sqrt{9a}\)

\(=5\sqrt{a}-20ab+5a.4\sqrt{a}b-6\sqrt{a}\)

\(=-\sqrt{a}-20ab+20a\sqrt{a}b\)

giúp tớ với ^.^

Góp ý chút. Cậu đăng tầm hai câu nhỏ một bài sẽ có nhiều người làm hơn đó.

g) \(\sqrt{\dfrac{a}{b}}+\sqrt{ab}-\dfrac{a}{b}\sqrt{\dfrac{b}{a}}=\sqrt{\dfrac{a}{b}}+\sqrt{ab}-\sqrt{\dfrac{a^2b}{ab^2}}\\ =\sqrt{\dfrac{a}{b}}+\sqrt{ab}-\sqrt{\dfrac{a}{b}}=\sqrt{ab}\)