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

Toán Lớp 5: (1+1/2)X(1=1/3)X(1+1/4)X(1+1/5)X-.X(1+1/x)=10091/2

Tháng Tư 19, 2023 Toán học 2 Comments 0 views

Toán Lớp 5: (1+1/2)X(1=1/3)X(1+1/4)X(1+1/5)X…..X(1+1/x)=10091/2

Comments ( 2 )

  1. trucoanh55
    trucoanh55
    19 Tháng Tư, 2023 at 5:52 sáng
    Reply
    @Tùng
    (1+1/2)+(1+1/3)+(1+1/4)+. . .+(1+1/x)=10091/2
    3/2+4/3+5/4+. . .+$\dfrac{x+1}{x}$=10091/2
    $\dfrac{3×4×5×. . .×(x+1)}{2×3×4×. . .×x}$=10091/2
    $\dfrac{x+1}{2}$=10091/2
    ⇒x+1=10091
    x=10091-1
    x=10090

  2. thienthanh
    thienthanh
    19 Tháng Tư, 2023 at 5:52 sáng
    Reply
    ( 1 + 1/2 ) xx ( 1 + 1/3 ) xx ( 1 + 1/4 ) xx ( 1 + 1/5 ) xx …. xx ( 1 + 1/x ) = 1009 1/2
    3/2 xx 4/3 xx 5/4 xx 6/5 xx …. xx ( x + 1 )/x = 2019/2
    ( 3 xx 4 xx 5 xx 6 xx …. xx ( x + 1 ) )/( 2 xx 3 xx 4 xx 5 xx …. xx x ) = 2019/2
    ( x + 1 )/2 = 2019/2
     x + 1 = 2019
          x  = 2019 – 1
          x  = 2018
    Vậy , x = 2018 .
    ________________________________________________________________________
    ( 1 + 1/2 ) xx ( 1 + 1/3 ) xx ( 1 + 1/4 ) xx ( 1 + 1/5 ) xx …. xx ( 1 + 1/x ) = 10091/2
    3/2 xx 4/3 xx 5/4 xx 6/5 xx …. xx ( x + 1 )/x = 10091/2
    ( 3 xx 4 xx 5 xx 6 xx …. xx ( x + 1 ) )/( 2 xx 3 xx 4 xx 5 xx …. xx x ) = 10091/2
    ( x + 1 )/2 = 10091/2
     x + 1 = 10091
          x  = 10091 – 1
          x  = 10090
    Vậy , x = 10090 .
     

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

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