3B = 3/2.5 + 3/5.8 +......+3/35.38
3B = 1/2 - 1/5 + 1/5 - 1/8 +......+ 1/35 - 1/38
3B = 1/2 - 1/38
3B = 18/38
B = 6/38 = 2/19
Vậy B = 2/19 nhé!
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tính A=\(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{92.95}+\frac{1}{95.95}\)
\(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+\frac{1}{14.17}+\frac{1}{17.20}\)
Tính: A = \(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+....+\frac{1}{92.95}+\frac{1}{95.98}\)
tìm x để \(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{10300}=\frac{1}{x}\)
a=\(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{65.68}\)
Tính nhanh
\(A=\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{98.101}\)
tính S= \(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+....+\frac{1}{47.50}\)
so sánh A với 1 , biếtA = \(\frac{1}{2.5}+\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+\frac{1}{14.17}+\frac{1}{17.20}\)
Tìm x:
\(\frac{3x}{2.5}+\frac{3x}{5.8}+\frac{3x}{8.11}+\frac{3x}{8.11}=\frac{1}{21}\)