Tính nhanh a,5×(1/5+1/17)-(1/5+2/17+6/10+9/51) b,44/7+38/5+78/9+37/4+2/5+5/7+1/3+3/4+1967

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1. Đáp án:

    a)12/17 b)36

   Giải thích các bước giải:

   a,5×(1/5+1/17)-(1/5+2/17+6/10+9/51)

   = 5x(1/5+1/5)+(1/5+6/10)+(2/17+9/51)

   = 5x(2/5+8/10+18/51)

   = 5x(6/5+6/17)

   = 5×6/5+6/17

   = 6+6/17

   = 12/17

   b,44/7+38/5+78/9+37/4+2/5+5/7+1/3+3/4+1967

   = (44/7+5/7)+(38/5+2/5)+(78/9+1/3)+(37/4+3/4)

   = 49/7+40/5+81/9+40/4

   = 7+8+9+10

   = 36

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