1/12+9/20-1/30-13/42+1/56 1/3+3/4+2/5+5/7+7/8+9/20+10/21+11/

1个回答

  • 1/12+9/20-1/30-13/42+1/56 =1/3-1/4+1/4+1/5-1/5+1/6-1/6-1/7+1/7-1/8=1/3-1/8=5/24

    1/3+3/4+2/5+5/7+7/8+9/20+10/21+11/24+19/35

    =1/ 3 +3 /4 +2 /5 +5 /7 +7/ 8 +(1/ 5 +1/ 4 )+(1/ 3 +1 /7 )+(1/ 3 +1 /8 )+(12 /35 +7 /35 ),

    =1 /3 +3 /4 +2/ 5 +5 /7 +7 /8 +(1/ 5 +1 /4 )+(1 /3 +1 /7 )+(1 /3 +1 /8 )+(1 /7 +1 /5 +1/ 5 ),

    =1 /3 ×3+(3/ 4 +1/ 4 )+(2 /5 +1 /5 ×3)+(5 /7 +1/ 7 ×2)+(7/ 8 +1 /8 ),

    =1+1+1+1+1,

    =5;