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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: 4\2×4 + 4\4×6 + 4\6×8 +–..+ 4\2008+2010

Toán Lớp 7: 4\2×4 + 4\4×6 + 4\6×8 +……….+ 4\2008+2010

Comments ( 2 )

  1. Giải đáp:
    1004/1005
    Lời giải và giải thích chi tiết:
    4/2.4+4/4.6+4/6.8+…+4/2008.2010
    =2.(2/2.4+2/4.6+2/6.8+…+2/2008.2010)
    =2.(1/2-1/4+1/4-1/6+1/6-1/8+…+1/2008-1/2010)
    =2.(1/2-1/2010)
    =1-1/1005
    =1004/1005

  2. Giải đáp:
    4/(2xx4)+4/(4xx6)+4/(6xx8)+…+4/(2008xx2010)
    =2xx(2/(2xx4)+2/(4xx6)+2/(6xx8)+…+2/(2008xx2010))
    =2xx((4-2)/(2xx4)+(6-4)/(4xx6)+(8-6)/(6xx8)+…+(2010-2008)/(2008xx2010))
    =2xx(1/2-1/4+1/4-1/6+1/6-1/8+…+1/2008-1/2010)
    =2xx[1/2+(-1/4+1/4)+(-1/6+1/6)+…+(-1/2008+1/2008)-1/2010]
    =2xx(1/2-1/2010)
    =2xx502/1005
    =1004/1005

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222-9+11+12:2*14+14 = ? ( )