Question

Tính M:

\(\frac{3}{1.5}+\frac{3}{5.9}+\frac{3}{9.13}+.............+\frac{3}{3993.3997}+\frac{3}{3997.4001}\)
 

Answer 1

3/1*5+3/5*9+3/9*13+.....+3/3993*3997+3/3997*4001

=1/3(1-1/5+1/5-1/9+1/9-1/13+....+1/3993-1/3997+1/3997-1/4001)

=1/3(1-1/4001)

=4000/12003

k nha

Answer 2

= 3/4(1-1/5+1/5-1/9+1/9-1/13+...+1/3993-1/3997+1/3997-1/4001)

=3/4(1-1/4001)

=3000/4001