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

Toán Lớp 6: so sánh A = 1/2^2+1/4^2+1/6^2+…+1/(2n)^2

Toán Lớp 6: so sánh A = 1/2^2+1/4^2+1/6^2+…+1/(2n)^2

Comments ( 1 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    A=1/2^2+1/4^2+1/6^2+…+1/(2n)^2
    =>A=1/2.2+1/4.4+1/6.6+…+1/(2n.2n)
    =>A<1/1.2+1/2.4+1/4.6+…+1/((2n-2).2n
    =>A<1/2.(1+2/2.4+2/4.6+…+2/((2n-2).2n))
    =>A<1/2.(1+1/2-1/4+1/4-1/6+…+1/(2n-2)-1/(2n))
    =>A<1/2.(1-1/(2n))
    =>A<1/2-1/(4n)<1/2
    =>A<1/2
    Vậy A<1/2

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

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