Gọi dãy trên là A
3/5A=3(4.7)+3/(7.10)+......+(3/(31+34)
=1/4-1/7+1/7-1/10+........+1/31-1/34
=1/4-1/34=15/68
Đúng 0
Bình luận (0)
Các câu hỏi tương tự
\(\frac{1}{4.7}+\frac{1}{7.10}+\frac{1}{10.13}+.....+\frac{1}{73.76}\)
\(\frac{4}{1.4}+\frac{4}{4.7}+\frac{4}{7.10}+\frac{4}{10.13}\)
tính nhanh:
\(\frac{5}{1.4}+\frac{5}{4.7}+\frac{5}{7.10}+.........+\frac{5}{100.103}\)
tìm x biết :
\(\frac{3x}{4.7}+\) \(\frac{3x}{7.10}+\)\(\frac{3x}{10.13}+\)\(\frac{3x}{13.16}+\)\(\frac{3x}{16.19}+\)\(\frac{3x}{19.22}=\)\(\frac{-5}{88}\)
cần gấp
Tính nhanh
\(A=\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+\frac{1}{10.13}+...+\frac{1}{97.100}\)
a)\(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+....+\frac{3}{2008.2011}\)\(\) b)\(\frac{-5}{1.6}-\frac{5}{6.11}-\frac{5}{11.16}-......-\frac{5}{2006.2011}\)
Tính :
\(A=\frac{3^2}{1.4}+\frac{3^2}{4.7}+\frac{3^2}{7.10}+\frac{3^2}{10.13}+\frac{3^2}{13.16}+...+\frac{3^2}{97.100}\)
Tìm A :
A = \(\frac{3^2}{1.4}+\frac{3^2}{4.7}+\frac{3^2}{7.10}+\frac{3^2}{10.13}+...+\frac{3^2}{97.100}\)
Tính nhanh:
a) \(A=\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+...+\frac{2}{31.34}\)
b) \(B=\frac{2}{1.2.3}+\frac{2}{2.3.4}+...+\frac{2}{100.101.102}\)