Cho biểu thức:
\(C=\frac{1}{2}x\frac{3}{4}x\frac{5}{6}x.....x\frac{79}{80}\)
Chứng minh C bé hơn \(\frac{1}{9}\)
Cho \(A=\frac{1}{2}.\frac{3}{4}.\frac{5}{6}.\frac{7}{8}.....\frac{79}{80}.CMR\)
\(A<\frac{1}{9}\)
Cho biểu thức: C=\(\frac{1}{2}\)x\(\frac{3}{4}\)x\(\frac{5}{6}\)x.....x\(\frac{79}{80}\). Chứng tỏ C<\(\frac{1}{9}\)
Mk đang cần câu trả lời gấp. ghi rõ cách trình bày cho mình mik tk cho! Thanks
Bài 1 : Tính
Cho A =\(\frac{1}{31}+\frac{1}{32}+\frac{1}{33}+......+\frac{1}{60}>\frac{7}{12}\)
B = \(\frac{1}{3^2}+\frac{1}{3^2}+\frac{1}{5^2}+......+\frac{ }{50^{21}}\)
CMR B >\(\frac{1}{4}\)và B < \(\frac{4}{9}\)
C = \(\frac{1}{2}.\frac{3}{4}.\frac{5}{6}.\frac{7}{8}.......\frac{79}{80}< \frac{1}{9}\)
a)\(\frac{7}{x}<\frac{x}{4}<\frac{10}{x}\)
b) Cho A=\(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{9^2}\). Chứng tỏ: \(\frac{8}{9}>A>\frac{2}{5}\)
bài 15 tìm x biết
a\(\frac{x}{4}-\frac{3}{7}+\frac{2}{5}=\frac{31}{140}\)
b\(\frac{5}{12}+\frac{5}{x}-\frac{1}{8}=\frac{1}{2}\)
c\(x+\frac{1}{9}-\frac{3}{5}=\frac{3}{6}\)
d\(\frac{3}{4}-x+\frac{6}{-11}=\frac{5}{6}\)
e\(x-\frac{1}{9}-\frac{3}{5}=\frac{3}{6}\)
Cho \(A=\frac{1}{2}.\frac{3}{4}.\frac{5}{6}...\frac{79}{80}\)và \(\frac{1}{9}\). Hãy so sánh
Bài 1:CMR:\(\frac{1}{4}+\frac{1}{5}+\frac{1}{6}+...+\frac{1}{15}<2\)
Bài 2: \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{x.\left(x+1\right)}=\frac{99}{101}\)
Bài 3:\(A=\frac{8}{9}.\frac{15}{16}.\frac{24}{25}.....\frac{2449}{2500}\)
Bài 4:CMR:\(1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{49}-\frac{1}{50}=\frac{1}{26}+\frac{1}{27}+\frac{1}{28}+...+\frac{1}{50}\)