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

Toán Lớp 5: (3/1.5+3/5.9+3/9.13+…+3/39.43

Home/ Toán Lớp 5: (3/1.5+3/5.9+3/9.13+…+3/39.43

Toán Lớp 5: (3/1.5+3/5.9+3/9.13+…+3/39.43

Tháng Tám 9, 2022 Toán học 2 Comments 0 views

Toán Lớp 5: (3/1.5+3/5.9+3/9.13+…+3/39.43

Comments ( 2 )

  1. diepbich93
    diepbich93
    9 Tháng Tám, 2022 at 12:57 sáng
    Reply
    Giải đáp:
    $\dfrac{126}{172}$
    Lời giải và giải thích chi tiết:
    $A=\dfrac3{1.5}+\dfrac3{5.9}+\dfrac3{9.13}\ +\,.\!.\!.+\ \dfrac{3}{39.43}\\\Rightarrow \dfrac A3=\dfrac{1}{1.5}+\dfrac{1}{5.9}+\dfrac1{9.13}\ +\,.\!.\!.+\ \dfrac{1}{39.43}\\\Rightarrow \dfrac{4A}{3}=\dfrac{4}{1.5}+\dfrac{4}{5.9}+\dfrac4{9.13}\ +\,.\!.\!.+\ \dfrac{4}{39.43}\\\Rightarrow \dfrac{4A}{3}=1-\dfrac15+\dfrac15-\dfrac19+\dfrac19-\dfrac1{13}\ +\,.\!.\!.+\ \dfrac{1}{39}-\dfrac{1}{43}\\\Rightarrow \dfrac{4A}{3}=1-\dfrac{1}{43}\\\Rightarrow \dfrac{4A}{3}=\dfrac{42}{43}\\\Rightarrow 4A=\dfrac{126}{43}\\\Rightarrow A=\dfrac{126}{172}$
    Vậy biểu thức có giá trị là $\dfrac{126}{172}$.

  2. haianhtu97
    haianhtu97
    9 Tháng Tám, 2022 at 12:57 sáng
    Reply
    ‘A.4/3=4/1.5+1/5.9+…+4/39.43
    A.4/3=1/1-1/5+1/5-1/9+…+1/39-1/43
    A . 4/3=1-1/43
    A.4/3=42/43
    A=42/43:4/3
    A=39/43

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

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