Question

Tính : B = 2/11.13 + 2/13.15 +...+2/99.101

Answer 1

\(B=\frac{2}{11.13}+\frac{2}{13.15}+...+\frac{2}{99.101}\)

\(B=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{99}-\frac{1}{101}\)

\(B=\frac{1}{11}-\frac{1}{101}\)

\(B=\frac{101}{1111}-\frac{11}{1111}\)

\(B=\frac{90}{1111}\)

Answer 2

B=1/11-1/13+1/13-1/15+...+1/99-1/101

B=1/11-1/101

B=90/101

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