Question

1/2.5+1/5.8+1/8.11+....+1/29.32

Answer 1

1/2.5+1/5.8+1/8.11+...+1/29.32 (khoảng cách từ 2-5;5-8;8-11;...;29-32 là 3) suy ra

=1/3(1/2-1/5+1/5-1/8+1/8-1/11+...+1/29-1/32)  (-1/5+1/5;-1/8+1/8;-1/11+1/11=0) suy ra =1/3(1/2-1/32)=1/3.15/32=5/32

Answer 2

1/2.5+1/5.8+1/8.9+............+1/29.32

=1/2-1/5+1/5-1/8+...............+1/29-1/32

=1/2-1/32

=15/32

ai tích mk=>mk tích lại