Các câu hỏi tương tự
CMR:\(\frac{7}{3}+\frac{11}{3^2}+\frac{15}{3^3}+...+\frac{2019}{3^{504}}< \frac{9}{2}\)
Cho A= \(\frac{7}{3}\)+ \(\frac{11}{3^2}\)+ \(\frac{15}{3^3}\)+ .......+ \(\frac{2019}{3^{504}}\). Chứng minh rằng A< \(\frac{9}{2}\)
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: \(\frac{8}{9}>A>\frac{2}{5}\)
B1: Thực hiện phép tính :a, 11frac{3}{4}-(6frac{5}{6}-4frac{1}{2})+1frac{2}{3}b, 2frac{17}{20}-1frac{11}{5}+6frac{9}{20}:3c, 4frac{3}{7}:left(frac{7}{5}.4frac{3}{7}right)d, left(3frac{2}{9}.frac{15}{23}.1frac{7}{29}right):frac{5}{23}B2: Thực hiện phép tính:a,11frac{3}{4}-(6frac{5}{6}4frac{1}{2}+1frac{2}{3})
b,left(5frac{7}{8}-2frac{1}{4}-0,5right):frac{23}{26}c,left(17frac{13}{15}-3frac{3}{7}right)-left(2frac{12}{15}-4right)
d,2frac{2}{3}.frac{-4}{5}.0,375-left(-10right).frac{-15}{24}
Đọc tiếp
B1: Thực hiện phép tính :
a, \(11\frac{3}{4}-(6\frac{5}{6}-4\frac{1}{2})+1\frac{2}{3}\)
b, \(2\frac{17}{20}-1\frac{11}{5}+6\frac{9}{20}:3\)
c, \(4\frac{3}{7}:\left(\frac{7}{5}.4\frac{3}{7}\right)\)
d, \(\left(3\frac{2}{9}.\frac{15}{23}.1\frac{7}{29}\right):\frac{5}{23}\)
B2: Thực hiện phép tính:
\(a,11\frac{3}{4}-(6\frac{5}{6}4\frac{1}{2}+1\frac{2}{3})\\ b,\left(5\frac{7}{8}-2\frac{1}{4}-0,5\right):\frac{23}{26}\)
\(c,\left(17\frac{13}{15}-3\frac{3}{7}\right)-\left(2\frac{12}{15}-4\right)\\ d,2\frac{2}{3}.\frac{-4}{5}.0,375-\left(-10\right).\frac{-15}{24}\)
Bài 4 :
a) Tính giá trị của biểu thức :
\(A=\left(\frac{1\frac{11}{31}\cdot4\frac{3}{7}-\left(15-6\frac{1}{3}\cdot\frac{2}{19}\right)}{4\frac{5}{6}+\frac{1}{6}\left(12-5\frac{1}{3}\right)}\cdot\left(-1\frac{14}{93}\right)\right)\cdot\frac{31}{50}\)
b) Chứng tỏ rằng : \(B=1-\frac{1}{2^2}-\frac{1}{3^2}-\frac{1}{3^2}-...-\frac{1}{2004^2}>\frac{1}{2004}\)
1) Tính nhanh
a) A=\(\frac{3}{11\text{x}13}+\frac{3}{13\text{x}15}+\frac{3}{15\text{x}17}+...+\frac{3}{97\text{x}99}\)
b) B=\(\frac{4}{7\text{x}31}+\frac{6}{7\text{x}11}+\frac{9}{10\text{x}41}+\frac{7}{10\text{x}57}\)
3) Chứng tỏ phân số \(\frac{8n+5}{6n+4}\)tối giản với mọi số nguyên khác 0
Cho \(A=\frac{5}{17}+\frac{-4}{9}-\frac{20}{31}+\frac{12}{17}-\frac{11}{31}\)
\(B=\frac{-3}{7}+\frac{7}{15}+\frac{-4}{7}+\frac{8}{15}+\frac{-2}{3}\)
Cho \(A=\frac{5}{17}+\frac{-4}{9}-\frac{20}{31}+\frac{12}{17}-\frac{11}{31}\)
\(B=\frac{-3}{7}+\frac{7}{15}+\frac{-4}{7}+\frac{8}{15}-\frac{-2}{3}\)
Tính số nguyên x sao cho \(A< \frac{x}{9}\le B\)
Tìm số nguyên x
a) \(\frac{1}{3}+\frac{-2}{5}+\frac{1}{6}+\frac{-1}{5}\le x< \frac{-3}{4}+\frac{2}{7}+\frac{-1}{4}+\frac{3}{5}+\frac{5}{7}\)
b)\(\frac{5}{17}+\frac{-9}{4}+\frac{-26}{31}+\frac{12}{17}+\frac{-11}{31}< \frac{x}{9}\le\frac{-3}{7}+\frac{7}{15}+\frac{4}{-7}+\frac{8}{15}\)