(81:√9+√169).√225 b. √(√7-1)^2-√7. c. √(5+√7)^2-√8-2√7

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1. Đáp án:

    `(81:sqrt{9}+sqrt{169}).sqrt{225}`

   `=(81:sqrt{3^2}+sqrt{13^2}).sqrt{15^2}`

   `=(81:3+13).15`

   `=(27+13).15`

   `=40.15`

   `=600`

   `b)sqrt{(sqrt7-1)^2}-sqrt7`

   `=|sqrt7-1|-sqrt7`

   `=\sqrt7-1-sqrt7`

   `=-1`

   `c)sqrt{(5+sqrt7)^2}-sqrt{8-2sqrt7}`

   `=|5+sqrt7|-sqrt{7-2sqrt7+1}`

   `=5+sqrt7-sqrt{(sqrt7-1)^2}`

   `=5+sqrt7-(sqrt7-1)`

   `=5+sqrt7-sqrt7+1=6`

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2. $Okokokokokok$

    

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