E=10/56 + 10/140 + 10/260 +...+10/1400
E=5/28+5/70+5/130+...+5/700
3E/5=3/4.7+3/7.10+3/10.13+...+3/25.28
3E/5=1/4-1/7+1/7-1/10+1/10-1/13+...+1/25-1/28
3E/5=1/4-1/28
3E/5=3/14
E=3/14.5/3
E=5/14
Vậy E=5/14
tính nhanh 10/56+10/140+10/260+...+10/1400
B = 10/56 + 10/140+10/260+.....+10/1400 ( phân số nha )
Tính B
Tính tổng:A=10/56+10/140+10/260+.........+10/1400
tính: 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
tính tong 10/56 + 10/140 + 10/260 + ..... + 10/1400
tinh nhanh
10/56+10/140+10/260+...+10/1400
Tính nhanh
a, 15/90.94 + 15/94.98 + 15/98.102 + ....... + 15/146.150
b, 10/56 + 10/140 + 10/260 + ...... + 10/1400
