Các câu hỏi tương tự
C/m ::
\(S=\frac{1}{12}+\frac{1}{13}+\frac{1}{14}+\frac{1}{15}+\frac{1}{16}+\frac{1}{17}+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}+\frac{1}{21}+\frac{1}{22}>\frac{1}{2}\)
Thực hiện so sánh:\(\frac{1}{12}+\frac{1}{13}+\frac{1}{14}+\frac{1}{15}+\frac{1}{16}+\frac{1}{17}\)\(+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}+\frac{1}{21}+\frac{1}{22}\)\(+\frac{1}{23}\)với \(\frac{5}{6}\)
\(\frac{1}{12}+\frac{1}{13}+\frac{1}{14}+...+\frac{1}{19}+\frac{1}{20}+\frac{1}{21}>\frac{5}{11}\)
Chưng Minh:\(\frac{1}{21}\)+\(\frac{1}{22}\)+\(\frac{1}{23}\)+....+\(\frac{1}{49}\)+\(\frac{1}{50}\)<\(1\frac{1}{12}\)
1. Tính nhanh
a, \(\frac{7}{13}.\frac{7}{15}-\frac{5}{12}.\frac{21}{39}+\frac{49}{91}.\frac{8}{15}\)
b, \(\left(\frac{12}{199}+\frac{23}{200}-\frac{34}{201}\right).\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\)
c,\(\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
Tính nhanh:
a,\(\frac{7}{13}\cdot\frac{7}{15}-\frac{5}{12}\cdot\frac{21}{39}+\frac{49}{91}\cdot\frac{8}{15}\)
b,\(\left(\frac{12}{199}+\frac{23}{200}-\frac{34}{201}\right)\cdot\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\)
Chứng minh rằng :
\(\frac{7}{12}< \frac{1}{21}+\frac{1}{20}+...+\frac{1}{40}< 1\)
Chú ý p/s thứ 2 là 1/20 chứ k phải 1/22 nha
Cho A=\(\frac{1}{25}\)n và b=\(\frac{7}{6}\)+\(\frac{13}{12}\)\(\frac{21}{20}\)+....+\(\frac{2451}{2450}\)
Tìm n để A+B=49
tính
\(\frac{-20}{21}.\frac{22}{35}+\frac{-20}{21}.\frac{13}{35}+\frac{-22}{21}\)