Câu hỏi của Nguyễn Hải Văn - Toán lớp 6 - Học toán với OnlineMath
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Các bạn giúp với :Bài 1:a, CMR: A dfrac{3}{1^2.2^2}+dfrac{5}{2^2.3^2}+dfrac{7}{3^2.4^2}+...+dfrac{21}{10^2.11^2} 1b, Cho B dfrac{3}{4}+dfrac{8}{9}+dfrac{15}{16}+dfrac{24}{25}+...+dfrac{2499}{2500}. CMR: B không phải là số nguyên.c, So sánh: C dfrac{2}{2^1}+dfrac{3}{2^2}+dfrac{4}{2^3}+...+dfrac{2021}{2^{2020}} với 3.
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Các bạn giúp với :<
Bài 1:
a, CMR: A = \(\dfrac{3}{1^2.2^2}+\dfrac{5}{2^2.3^2}+\dfrac{7}{3^2.4^2}+...+\dfrac{21}{10^2.11^2}< 1\)
b, Cho B = \(\dfrac{3}{4}+\dfrac{8}{9}+\dfrac{15}{16}+\dfrac{24}{25}+...+\dfrac{2499}{2500}.\) CMR: B không phải là số nguyên.
c, So sánh: C = \(\dfrac{2}{2^1}+\dfrac{3}{2^2}+\dfrac{4}{2^3}+...+\dfrac{2021}{2^{2020}}\) với 3.
ko dùng máy tính
\(\dfrac{1}{7}+\dfrac{1}{8}+\dfrac{1}{9}+\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}+\dfrac{1}{14}+\dfrac{1}{15}+\dfrac{1}{18}+\dfrac{1}{22}+\dfrac{1}{24}+\dfrac{1}{28}+\dfrac{1}{33}\)
Chứng minh rằng P>3 biet P= \(\dfrac{5}{2×1}+\dfrac{4}{1×11}+\dfrac{3}{11×2}+\dfrac{1}{2×15}+\dfrac{13}{15×4}+\dfrac{15}{4×43}+\dfrac{13}{43×8}\)
so sanh
M=\(\left(\dfrac{1}{2^2}-1\right).\left(\dfrac{1}{3^2}-1\right).\left(\dfrac{1}{4^2}-1\right)...\left(\dfrac{1}{100^2}-1\right)\)va \(\dfrac{1}{2}\)
B=\(\dfrac{1}{20}+\dfrac{1}{21}+...+\dfrac{1}{200}va\dfrac{9}{10}\)
C=\(\dfrac{10}{17}+\dfrac{8}{15}+\dfrac{11}{16}va2\)
Tính hợp lý :
a,\(\left(\dfrac{136}{15}-\dfrac{28}{5}+\dfrac{62}{10}\right).\dfrac{21}{24}\)
b,\(\dfrac{3}{11}.\dfrac{4}{11}+\left(\dfrac{3}{13}.\dfrac{4}{11}-\dfrac{1}{13}\right)\)
CMR \(1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{5}-\dfrac{1}{6}+...+\dfrac{1}{19}-\dfrac{1}{20}=\dfrac{1}{11}+\dfrac{1}{12}+\dfrac{1}{13}+...+\dfrac{1}{20}\)
Bài 1: tính
Cho A dfrac{1}{31}+dfrac{1}{32}+dfrac{1}{33}+........+dfrac{1}{60}dfrac{7}{12}
Bdfrac{1}{3^2}+dfrac{1}{3^2}+dfrac{1}{5^2}+.....+dfrac{1}{50^2}
CMR B dfrac{1}{4}; B dfrac{4}{9}
C dfrac{1}{2}.dfrac{3}{4}.dfrac{5}{6}.dfrac{7}{8}...........dfrac{79}{80}dfrac{1}{9}
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Bài 1: tính
Cho A= \(\dfrac{1}{31}+\dfrac{1}{32}+\dfrac{1}{33}+........+\dfrac{1}{60}>\dfrac{7}{12}\)
B=\(\dfrac{1}{3^2}+\dfrac{1}{3^2}+\dfrac{1}{5^2}+.....+\dfrac{1}{50^2}\)
CMR B > \(\dfrac{1}{4}\); B < \(\dfrac{4}{9}\)
C = \(\dfrac{1}{2}.\dfrac{3}{4}.\dfrac{5}{6}.\dfrac{7}{8}...........\dfrac{79}{80}\)<\(\dfrac{1}{9}\)
\(\dfrac{-4}{11}\times\dfrac{7}{15}-\dfrac{4}{15}\times\dfrac{8}{11}+\dfrac{-5}{11}\)
\(2\dfrac{2}{3}-2\dfrac{3}{5}\times\dfrac{10}{7}-\dfrac{7}{5}\)
các bạn làm trong hôm nay dùm mình nhé, cảm ơn
1. tính
a. dfrac{3}{5}-dfrac{2}{3}+dfrac{16}{15}
b. (dfrac{5}{6}-dfrac{4}{5}):dfrac{7}{30}-dfrac{6}{7}
c. dfrac{4}{11}.dfrac{-2}{9}+dfrac{4}{11}.dfrac{-8}{9}+dfrac{4}{11}.dfrac{1}{9}
d.dfrac{-13}{10}-dfrac{15}{16}:dfrac{-3}{4}+dfrac{21}{25}.dfrac{-15}{28}
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1. tính
a. \(\dfrac{3}{5}\)-\(\dfrac{2}{3}\)+\(\dfrac{16}{15}\)
b. (\(\dfrac{5}{6}\)-\(\dfrac{4}{5}\)):\(\dfrac{7}{30}\)-\(\dfrac{6}{7}\)
c. \(\dfrac{4}{11}\).\(\dfrac{-2}{9}\)+\(\dfrac{4}{11}\).\(\dfrac{-8}{9}\)+\(\dfrac{4}{11}\).\(\dfrac{1}{9}\)
d.\(\dfrac{-13}{10}\)-\(\dfrac{15}{16}\):\(\dfrac{-3}{4}\)+\(\dfrac{21}{25}\).\(\dfrac{-15}{28}\)