Bài 1 :Tính tỉ số A/B biết
a) \(A=\frac{4}{7\cdot31}+\frac{6}{7\cdot41}+\frac{9}{10\cdot41}+\frac{7}{10\cdot57}\)
\(B=\frac{7}{19\cdot31}+\frac{5}{19\cdot43}+\frac{3}{23\cdot43}+\frac{11}{23\cdot57}\)
b)\(A=\frac{40}{31\cdot39}+\frac{35}{39\cdot46}+\frac{30}{46\cdot52}+\frac{25}{52\cdot57}\)
\(B=\frac{91}{19\cdot31}+\frac{65}{19\cdot43}+\frac{39}{989}+\frac{143}{1311}\)
Bài 2 : Tính Avà B biết :
a) \(A=\frac{2006}{1\cdot2}+\frac{2006}{2\cdot3}+...+\frac{2006}{2006\cdot2007}\)
\(B=\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+...+\frac{1}{2004\cdot2005\cdot2006}\)
