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Gíup mình nha,các thiên tài !
Tính tổng sau:A=\(\dfrac{25}{18.21}+\dfrac{25}{21.24}+\dfrac{25}{24.27}+.....+\dfrac{25}{123.126}\)
\(\dfrac{1}{28.21}+\dfrac{1}{21.24}+\dfrac{1}{24.27}+...+\dfrac{1}{123.126}\)
Thực hiện phép tính sau:
\(A=\dfrac{5}{12.17}+\dfrac{35}{17.18}-\dfrac{39}{18.21}+\dfrac{30}{21.72}\)
[Bài này nhiều câu lắm, những 12 câu cơ, sợ các bạn thấy dài là nản! Tí nữa đăng tiếp! - 03/12 câu]
Tính tổng sau bằng phương pháp hợp lý nhất:
1) A = \(\dfrac{5^2}{1.6}\) + \(\dfrac{5^2}{6.11}\) + ... + \(\dfrac{5^2}{26.31}\)
2) B = \(\dfrac{6}{15.18}\) + \(\dfrac{6}{18.21}\) + \(\dfrac{6}{21.24}\) + ... + \(\dfrac{6}{87.90}\)
3) C = \(\dfrac{3^2}{8.11}\) + \(\dfrac{3^2}{11.14}\) + ... + \(\dfrac{3^2}{197.200}\)
Các bạn cố gắng giải đầy đủ giúp mình!
tính nhanh :
a) \(6\dfrac{5}{7}-\left(1\dfrac{3}{4}+2\dfrac{5}{7}\right)\)
b) \(7\dfrac{5}{11}-\left(2\dfrac{3}{7}+3\dfrac{5}{11}\right)\)
c) \(\dfrac{1}{3}.\dfrac{4}{5}+\dfrac{1}{3}.\dfrac{6}{5}-\dfrac{4}{3}\)
d) \(\left(\dfrac{-4}{5}+\dfrac{4}{3}\right)+\left(\dfrac{-5}{4}+\dfrac{14}{5}\right)-\dfrac{7}{3}\)
e) \(\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{14}+1\dfrac{5}{7}\)
\(Tính: B = \dfrac{2 - \dfrac{2}{19} + \dfrac{2}{43} - \dfrac{2}{2017}}{3 - \dfrac{3}{19} + \dfrac{3}{43} - \dfrac{3}{2017}} :\dfrac{4 - \dfrac{4}{29} + \dfrac{4}{41} - \dfrac{4}{2018}}{5 - \dfrac{5}{29} + \dfrac{5}{41} - \dfrac{5}{2018}} \)
1) \(A=\dfrac{1}{5}+\dfrac{2}{5^2}+\dfrac{3}{5^3}+\dfrac{4}{5^4}+...+\dfrac{500}{5^{500}}< \dfrac{5}{16}\)
\(\dfrac{3}{54}+\dfrac{5}{126}+\dfrac{7}{294}:\dfrac{5}{24}+\dfrac{5}{104}+\dfrac{5}{234}\)
\(A=\dfrac{5-\dfrac{5}{29}+\dfrac{5}{41}-\dfrac{5}{2941}}{3-\dfrac{3}{19}+\dfrac{3}{43}-\dfrac{3}{1943}}:\dfrac{4-\dfrac{4}{29}+\dfrac{4}{41}-\dfrac{4}{2941}}{2-\dfrac{2}{19}+\dfrac{2}{43}-\dfrac{2}{1943}}\)
Rút gọn