Tính nhanh : a)4/5+6/5-8/10+12/15 b)43.7+29.57+13.43+57

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1. `a//`

   `(4)/(5)+(6)/(5)-(8)/(10)+(12)/(15)`

   `=((4)/(5)+(6)/(5))-((8)/(10)-(12)/(15))`

   `=(10)/(5)-((24)/(30)-(24)/(30))`

   `=2-(0)/(30)`

   `=2-0`

   `=2`

   `b//`

   `43+29,57+13,43+57`

   `=(43+57)+(29,57+13,43)`

   `=100+43`

   `=143`

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2. Đáp án:

   $a/$ `4/5 + 6/5 – 8/10 + 12/15`

   `= (4/5 + 6/5 + 12/15) – 8/10`

   `= (10/5 + 12/15) – 8/10`

   `= 14/5 – 8/10`

   `= 2`

   $b/$ `43 + 29,57 + 13,43 + 57`

   `= (43 + 57) + (29,57 + 13,43)`

   `= 100 + 43`

   `= 143`

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