a,25^3: 5^2 b,(3/7)^21: (9/49)^6 c, 3-(-6/7)^0 +(1/2)^2 :2

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1. `\text{a)}`

   `25^3 : 5^2`

   `= (5^2)^3 : 5^2`

   `= 5^6 : 5^2`

   `= 5^4`

   `\text{b)}`

   `(3/7)^21 : (9/49)^6`

   `= (3/7)^21 : [(3/7)^2]^6`

   `= (3/7)^21 : (3/7)^12`

   `= (3/7)^9`

   `\text{c)}`

   `3 – (-6/7)^0 + (1/2)^2 :2`

   `= 3 – 1 + 1/4 :2`

   `= 2 + 1/8`

   `=17/8` 

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2. Đáp án:

   `a,`

   `25^3 ÷ 5^2`

   `= (5^2)^3 ÷ 5^2`

   `= 5^6 ÷ 5^2`

   `= 5^4`

   $\\$

   `b,`

   `(3/7)^{21} ÷ (9/49)^6`

   `= (3/7)^{21} ÷ [(3/7)^2]^6`

   `= (3/7)^{21} ÷ (3/7)^{12}`

   `= (3/7)^{9}`

   $\\$

   `c,`

   `3 – (-6/7)^0 + (1/2)^2 ÷ 2`

   `3 – 1 + 1/4 × 1/2`

   `= 3 – 1 + 1/8`

   `= 2 + 1/8`

   `= 16/8 + 1/8`

   `= 17/8`

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