Đại số lớp 6

TV

\(\dfrac{3}{4.7}+\dfrac{4}{7.11}+\dfrac{5}{11.16}+...+\dfrac{14}{92.106}\)

TT
30 tháng 3 2017 lúc 16:49

\(=\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+...+\dfrac{1}{92}-\dfrac{1}{106}\)

\(=\dfrac{1}{4}-\dfrac{1}{106}=\dfrac{51}{212}\)

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NN
30 tháng 3 2017 lúc 17:06

\(\dfrac{3}{4.7}+\dfrac{4}{7.11}+\dfrac{5}{11.16}+...+\dfrac{14}{92.106}\)
= \(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{16}+...+\dfrac{1}{92}-\dfrac{1}{106}\)
= \(\dfrac{1}{4}-\dfrac{1}{106}\)
= \(\dfrac{51}{212}\)

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