Question

giúp mình bài 4 với bài 5 với ạ

Answer 1

Bài 5:

a: \(=x-\sqrt{xy}+y-\sqrt{xy}=x-2\sqrt{xy}+y=\left(\sqrt{x}-\sqrt{y}\right)^2\)

b: \(=\dfrac{\sqrt{a}\left(\sqrt{a}+\sqrt{b}\right)}{\sqrt{b}\left(\sqrt{a}+\sqrt{b}\right)}=\sqrt{\dfrac{a}{b}}\)

c: \(=\dfrac{\sqrt{xy}\left(x-y\right)}{\sqrt{xy}}=x-y\)

Answer 2

Bài `4:`

`a)\sqrt{125}-4\sqrt{45}+3\sqrt{20}-\sqrt{80}`

`=5\sqrt{5}-12\sqrt{5}+6\sqrt{5}-4\sqrt{5}`

`=-5\sqrt{5}`

~~~~~~~~~~~~~~~

`b)2\sqrt{27/4}-\sqrt{48/9}-2/5\sqrt{75/16}`

`=3\sqrt{3}-4/\sqrt{3}-\sqrt{3}/2`

`=[18-8-3]/[2\sqrt{3}]`

`=7/[2\sqrt{3}]=[7\sqrt{3}]/6`

~~~~~~~~~~~~~~~~

`c)2\sqrt{9/8}-\sqrt{49/2}+\sqrt{25/18}`

`=3/\sqrt{2}-7/\sqrt{2}+5/[3\sqrt{2}]`

`=[9-21+5]/[3\sqrt{2}]`

`=[-7]/[3\sqrt{2}]=[-7\sqrt{2}]/6`

~~~~~~~~~~~~~~~~~~

`d)5\sqrt{20}-3\sqrt{12}+15\sqrt{1/5}-4\sqrt{27}+\sqrt{\sqrt{5^2-4^2}}`

`=10\sqrt{5}-6\sqrt{3}+3\sqrt{5}-12\sqrt{3}+\sqrt{\sqrt{(5-4)(5+4)}}`

`=13\sqrt{5}-18\sqrt{3}+\sqrt{\sqrt{9}}`

`=13\sqrt{5}-18\sqrt{3}+\sqrt{3}`

`=13\sqrt{5}-17\sqrt{3}`

~~~~~~~~~~~~~~~~~~~~~~

`e)\sqrt{7+4\sqrt{3}}+\sqrt{28-10\sqrt{3}}`

`=\sqrt{(2+\sqrt{3})^2}+\sqrt{(5-\sqrt{3})^2}`

`=|2+\sqrt{3}|+|5-\sqrt{3}|`

`=2+\sqrt{3}+5-\sqrt{3}=7`

 

Answer 3

còn b4 ai giúp t với ạ:")