cho mình hỏi câu a b c làm như nào ạ ;33

`#Thao` `Bý`

`a)`

`\sqrt{45} - 13\sqrt{5} + \sqrt{80} - \sqrt{125}`

`=\sqrt{9.5} - 13\sqrt{5}+ \sqrt{16.5 }- \sqrt{5^2 .5}`

`=3\sqrt{5} - 13\sqrt{5} + 4\sqrt{5} - 5\sqrt{5}`

`=`` (3-13+4-5)\sqrt5`

`=``-11\sqrt{5}`

`b)`

`\sqrt{32}+``\sqrt{62}/\sqrt{31}-``12\sqrt{1/2} +``6/\sqrt{2}`

`=\sqrt{16.2} + \sqrt{62/31}-12.``1/2\sqrt{2}+3\sqrt{2}`

`=4\sqrt{2} + \sqrt{2}-6 \sqrt{2}+3 \sqrt{2}`

`=(4+1-6+3)``\sqrt{2}`

`=2``\sqrt{2}`

`c)` 

`(\sqrt{10}-\sqrt{5})/(\sqrt{2}-1)``-\sqrt{(-2)^2 . 5}+\sqrt{(\sqrt{5}-2)^2}`

`=(\sqrt{5}(\sqrt{2}-1))/(\sqrt{2}-1)-|-2|.\sqrt{5}+|\sqrt{5}-2|`

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

`=``-2`