b)
\(5\left(\frac{5}{1.6}+\frac{5}{6.11}+...+\frac{5}{26.31}\right)\)
\(5\left(1-\frac{1}{6}+...+\frac{1}{26}-\frac{1}{31}\right)\)
\(5\left(1-\frac{1}{31}\right)\)
\(=\frac{150}{31}\)
a)
\(\frac{7}{10}-\frac{7}{11}+...+\frac{7}{69}-\frac{7}{70}\)
\(=\frac{7}{10}-\frac{7}{70}\)
\(=\frac{3}{5}\)
tính nhanh
\(\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}+...+\frac{7}{69.70}\) số cuối là số 69.70 nha
các bn giúp nha
\(A=\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}+...+\frac{7}{69.70}\)
\(B=\frac{1}{18}+\frac{1}{54}+\frac{1}{108}+...+\frac{1}{990}\)
\(C=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+...+\frac{89}{90}\)
\(\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}+...+\frac{7}{69.70}\)
\(a=\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}.....+\frac{7}{69.70}\)
\(A=\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}+...+\frac{7}{69.70}\)
\(\frac{7}{10.11}\)+\(\frac{7}{11.12}\)+\(\frac{7}{12.13}\)+...+\(\frac{7}{69.70}\)
Tính tổng sau
Bạn nào giải giúp mình với ^^.
I/ Tính Nhanh.
1/ (1 - \(\frac{1}{2^2}\)) . (1 - \(\frac{1}{3^2}\)) . (1 - \(\frac{1}{4^2}\)) . .... . (1 -\(\frac{1}{10^2}\))
2/ \(\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}+...+\frac{7}{69.70}\)
Tính
a)\(\left(17\frac{13}{15}-3\frac{3}{7}\right)-\left(2\frac{12}{15}-4\right)\)
b) \(\left(3\frac{2}{9}.\frac{15}{23}.1\frac{7}{29}\right):\frac{5}{23}\)
c)\(2\frac{17}{20}-1\frac{11}{5}+6\frac{9}{20}:3\)
giúp mik với ,mik đag cần gấp.Tks
Tính nhanh
1)A=\(\frac{7}{10.11}+\frac{7}{11.12}+\frac{7}{12.13}+...+\frac{7}{69.70}\)
2)B=\(\frac{1}{25.27}+\frac{1}{27.29}+\frac{1}{29.31}+...+\frac{1}{73.75}\)
3)C=\(\frac{4}{2.4}+\frac{4}{4.6}+\frac{4}{6.8}+...+\frac{4}{2008.2010}\)
