B=1/14+1/35+1/65+1/350
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Tính S =1/14+1/35+1/65+...+1/350
`Answer:`
\(S=\frac{1}{14}+\frac{1}{35}+\frac{1}{65}+...+\frac{1}{350}\)
\(\Rightarrow S=\frac{2}{28}+\frac{2}{70}+\frac{2}{130}+...+\frac{2}{700}\)
\(\Rightarrow S=\frac{2}{4.7}+\frac{2}{7.10}+\frac{2}{10.13}+...+\frac{2}{25.28}\)
\(\Rightarrow S=\frac{2}{3}\left(\frac{1}{4.7}+\frac{1}{7.10}+\frac{1}{10.13}+...+\frac{1}{25.28}\right)\)
\(\Rightarrow S=\frac{2}{3}\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+...+\frac{1}{25}-\frac{1}{28}\right)\)
\(\Rightarrow S=\frac{2}{3}.\frac{3}{14}\)
\(\Rightarrow S=\frac{1}{7}\)
tính B=1/2+1/14+1/35+1/65+1/4950.
a) Tính hợp lí các tổng sau:
S1: 1/14+1/35+1/65+.....+1/350
S2: 1/3+1/32+1/33+1/34+.....+1/3300
S3:1/1x3x5+1/3x5x7+1/5x7x9+....+1/25x27x29
S4:1+1/2+1/4+1/8+....+1/1024
b) Tìm x biết
(1/1x101+1/2x102+....+1/10x110)x=1/1x11+1/2x12+...+1/100x110
E=1/2+1/14+1/35+1/65+...+1/527
E=1/2+1/14+1/35+1/65+...+1/527
1/2+1/14+1/35+1/65+1/104+1/152 = ?
1/2+1/14+1/35+1/65+1/104+1/152= 12/19.
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1/2+1/14+1/35+1/65+1/104+1/152
đây là bài tính nhanh , mong các bạn giúp đỡ
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1/2+1/14+1/35+1/65+1/104+1/152
a=1/2+1/14+1/35+1/65+1/104+1/152