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

Toán Lớp 6: 1/1x2x3+1/2x3x4+1/3x4x5+…+1/10x11x12

Toán Lớp 6: 1/1x2x3+1/2x3x4+1/3x4x5+…+1/10x11x12

Comments ( 2 )

  1. Đặt:
    A = 1/(1 × 2 × 3) + 1/(2 × 3 × 4) + 1/(3 × 4 × 5) + … + 1/(10 × 11 × 12)
    2A = 2 × (1/(1 × 2 × 3) + 1/(2 × 3 × 4) + 1/(3 × 4 × 5) + … + 1/(10 × 11 × 12))
    2A = 1/(1 × 2) × 1/(3 × 4) + 1/(3 × 4 × 5) + … + 1/(10 × 11 × 12)
    2A = 1/2 – 1/(2 × 3) + 1/(3 × 4) – 1/(4 × 5) + … + 1/(10 × 11) – 1/(11 × 12)
    2A = 1/2 – 1/(11 × 12)
    2A = 1/2 – 1/132
    2A = 65/132
    A = 65/132 : 1/2
    A = 65/264
     

  2. Giải đáp + Lời giải và giải thích chi tiết :
    1/ 1 × 2 × 3 + 1/ 2 × 3 × 4 + 1/ 3 × 4 × 5 + … + 1/ 10 × 11 × 12
    = 1/2 – 1/ 11 × 12
    = 65/132
    NO COPY
    @nguyenmai093
                 Cho mik xin vote, cám ơn, câu trả lời hay nhất với ạ !             

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

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