tính nhanh A=1/45 + 2/45 + 1/15 + 4/45 + 1/9 + 2/15 + 7/45 + 8/45 + 1/5 B= 1/28 + (-1)/14 + 3/28 + 1/7 + (-5)/28 + 3/14 + (-1)/4

0 bình luận về “tính nhanh A=1/45 + 2/45 + 1/15 + 4/45 + 1/9 + 2/15 + 7/45 + 8/45 + 1/5 B= 1/28 + (-1)/14 + 3/28 + 1/7 + (-5)/28 + 3/14 + (-1)/4”

1. `A=1/45 + 2/45 + 1/15 + 4/45 + 1/9 + 2/15 + 7/45 + 8/45 + 1/5`

   `A=(1/45+2/45+4/45+7/45+8/45)+(1/15+1/9+2/15+1/5)`

   `A=22/45+(3/45+5/45+6/45+9/45)`

   `A=22/45+23/45`

   `A=1`

   `B= 1/28 + (-1)/14 + 3/28 + 1/7 + (-5)/28 + 3/14 + (-1)/4`

   `B=(1/28+3/28+(-5)/28)+((-1)/14+1/7+3/14+(-1)/4)`

   `B=(-1)/28+((-2)/28+4/28+6/28+(-7)/28)`

   `B=(-1)/28+1/28`

   `B=0`

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2. Đáp án:

    

   Giải thích các bước giải:

   A=1/45+2/45+1/15+4/45+1/9+2/15+7/45+8/45+1/5

      =1/45+2/45+3/45+4/45+5/45+6/45+7/45+8/45+9/45

      =1+2+3+4+5+6+7+8+9

   ____________________________________

                        45

      =(1+9)+(2+8)+(3+7)+(4+6)+5

   ___________________________________________

                            45

      =10*4+5

   _____________

          45

      =45/45

      =1

   B=1/28+(-1)/14+3/28+1/7+(-5)/28+3/14+(-1)/4

     =1/28+(-2)/28+3/28+4/28+(-5)/28+6/28+(-7)/28

     =1+(-2)+3+4+(-5)+6+(-7)

   ______________________________________

                            28

     =1+(3-2)-(5-4)-(7-6)  

   _______________________________________

                     28

     =1+1-1-1

   _______________________________________

          28

   =0

   #Chiell-))

   #Xin_câu_trả_lời_hay_nhất

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