tính

a, \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+-..+\dfrac{1}{9500}\)

b, \(\dfrac{3}{2}-\dfrac{5}{6}-\dfrac{7}{12}-\dfrac{9}{20}--.-\dfrac{19}{90}\)

Các câu hỏi liên quan