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

Toán Lớp 8: B=$\frac{3}{2.5}$ +$\frac{3}{5.8}$+$\frac{3}{8.11}$+…+ $\frac{3}{47.50}$

Tháng Bảy 12, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: B=$\frac{3}{2.5}$ +$\frac{3}{5.8}$+$\frac{3}{8.11}$+…+ $\frac{3}{47.50}$

Comments ( 2 )

  1. bichquyenlien
    bichquyenlien
    12 Tháng Bảy, 2022 at 2:51 sáng
    Reply
    Giải đáp:
    $B=\dfrac{12}{25}$
    Lời giải và giải thích chi tiết:
    $^{\large*}\dfrac{a}{b\,.c}=\dfrac1b-\dfrac 1c\, (c-b=a)\\B=\dfrac3{2.5}+\dfrac3{5.8}+\dfrac3{8.11}\ +\,.\!.\!.+\ \dfrac3{47.50}\\\Rightarrow B=\dfrac{1}{2}-\dfrac15+\dfrac15-\dfrac18+\dfrac18-\dfrac{1}{11}\ +\,.\!.\!.+\ \dfrac{1}{47}-\dfrac{1}{50}\\\Rightarrow B=\dfrac{1}{2}-\dfrac{1}{50}\\\Rightarrow B=\dfrac{12}{25}$

  2. giangnguyen33
    giangnguyen33
    12 Tháng Bảy, 2022 at 2:51 sáng
    Reply
    #huy
    B=3/(2.5)+3/(5.8)+3/(8.11)+…+3/(47.50)
    =1/2-1/5+1/5-1/8+1/8+1/11+…+1/47-1/50
    =1/2-1/50
    =12/25
    ->B=12/25
     

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

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