Tuyển Cộng tác viên Hoc24 nhiệm kì 26 tại đây: https://forms.gle/dK3zGK3LHFrgvTkJ6
gọi bt trên là A
ta có 3/10A=6/112+6/280+.........+6/2800
=6/8*14+6/14*20+.....+6/50*56
=1/8-1/14+1/14-1/20+........+1/50-1/56
=1/8-1/56=3/28
suy ra A=3/28*10/3=5/14
tích hộ nha
5/14 nha
HT
@@@@@@@@@@@@@@@
H = 10/56+10/140+10/260+10/1400
10/56+10/140+10/260+.....+10/1400
Tính tổng:A=10/56+10/140+10/260+.........+10/1400
10/56+10/140+10/260+...+10/1400
A=-10/56+-10/140+-10/260+...+-10/1400
tính: 10/56+10/140+10/260+...+10/1400
A=10/56+10/140+10/260+......+10/1400
tính tổng M=\(\dfrac{10}{56}+\dfrac{10}{140}+\dfrac{10}{260}+....+\dfrac{260}{1400}\)
Tính tổng : 10/56 + 10/140 + 10/260...+10/1400
