Bài 1: Tính tích:
\(\dfrac{3}{2^2}\). \(\dfrac{8}{3^2}\). \(\dfrac{15}{4^2}\)...\(\dfrac{899}{30^2}\)
Bài 2:Tính tổng:
\(\dfrac{1}{1.2.3}\)+\(\dfrac{1}{2.3.4}\)+\(\dfrac{1}{3.4.5}\)+...+\(\dfrac{1}{37.38.39}\)
Bài 3:Tính tổng sau: A= \(\dfrac{5}{18.21}\)+\(\dfrac{5}{21.24}\)+\(\dfrac{5}{24.27}\)+...+\(\dfrac{5}{123.126}\)
GIÚP MÌNH VỨ NHEN. HIHI