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

Toán Lớp 8: Tính `S=1/2+1/6+1/12+1/20+-+1/2450` Héo me kẻo me héo mất

Toán Lớp 8: Tính S=1/2+1/6+1/12+1/20+….+1/2450
Héo me kẻo me héo mất

Comments ( 2 )

  1. S = $\frac{1}{2}$ + $\frac{1}{6}$ + $\frac{1}{12}$ + $\frac{1}{20}$ + … + $\frac{1}{2450}$ 
    S = $\frac{1}{1×2}$ + $\frac{1}{2×3}$ + $\frac{1}{3×4}$ + $\frac{1}{4×5}$ + … + $\frac{1}{49×50}$
    S = 1 – $\frac{1}{2}$ + $\frac{1}{2}$ – $\frac{1}{3}$ + $\frac{1}{3}$ – $\frac{1}{4}$ + $\frac{1}{4}$ – $\frac{1}{5}$ + … + $\frac{1}{49}$ – $\frac{1}{50}$ 
    S = 1 – $\frac{1}{50}$ = $\frac{49}{50}$ 
     

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