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

Toán Lớp 6: 1 × 2 + 2 × 3 + 3 × 4 + 4 × 5 + 5 × 6 +-.+ 2002 × 2003

Tháng Sáu 21, 2022 Toán học 1 Comment 0 views

Toán Lớp 6: 1 × 2 + 2 × 3 + 3 × 4 + 4 × 5 + 5 × 6 +…..+ 2002 × 2003

Comments ( 1 )

  1. tuminh25
    tuminh25
    21 Tháng Sáu, 2022 at 10:55 chiều
    Reply
    Gọi 1 .2+2.3+3.4+4.5+5.6+…+2002.2003 là A
    A = 1 .2+2.3+3.4+4.5+5.6+…+2002.2003
    => 3A = 1.2.3 + 2.3.(4-1) + 3.4.(5-2)+4.5.(6-3) + 5.6.(7-4) + … + 2002.2003 .(2004 – 2001)
    => 3A = 1.2.3 + 2.3.4 – 1.2.3 + 3.4.5 – 2.3.4 + 4.5.6 – 3.4.5 + 5.6.7 – 4.5.6 + … + 2002 . 2003.2004 – 2001.2002.2003
    => 3A = 2002.2003.2004
    => A  = \frac{2002.2003.2004}{3}
    => A = 2678684008
     

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

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