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

Toán Lớp 7: Tính nhanh : A=1/3.5-1/5.7-…-1/97.99

Toán Lớp 7: Tính nhanh :
A=1/3.5-1/5.7-…-1/97.99

Comments ( 1 )

  1. Giải đáp:
    A= $\frac{1}{2}$ ($\frac{2}{3.5}$ + $\frac{2}{5.7}$ +…+ $\frac{2}{97.99}$)
    A= $\frac{1}{2}$ ($\frac{1}{3}$ – $\frac{1}{5}$ + $\frac{1}{5}$ – $\frac{1}{7}$ +…+ $\frac{1}{97}$ – $\frac{1}{99}$) 
    A= $\frac{1}{2}$ ($\frac{1}{3}$ – $\frac{1}{99}$)
    A= $\frac{1}{2}$.$\frac{32}{99}$
    A= $\frac{16}{99}$ 
    Vậy A=$\frac{16}{99}$
    Xin hay nhất nha

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