= 3/2 . 4/3 . 5/4 . .... 1000/999
= \(\frac{3.4.5...1000}{2.3.4.....999}=\frac{\left(3.4.5....999\right).1000}{2\left(3.4.5....999\right)}=\frac{1000}{2}=500\)
A=1/1×2+1/3×4+1/4×5+...1/999×1000
B=1/501×1000+1/502×999+...+1/999×502+1/1000×501
Tính A/B
1*1/2*1*1/3*1*1/4*...*1*1/999
1/1*2*3+1/2*3*4+1/3*4*5+.........+1/998*999*1000
tính tổng
s(1): 1+2+3+.............+999
s(2):1+4+7+..........+79
s(3): 1+10+20+.................+999
s(4): 1+3+5+..........100
Tính\(\frac{1}{1}.\frac{1}{2}+\frac{1}{2}.\frac{1}{3}+\frac{1}{3}.\frac{1}{4}+............+\frac{1}{998}.\frac{1}{999}+\frac{1}{999}.\frac{1}{1000}\)
(1\2+1).(1\3+1).(1\4+1)......(1\999+1)
(1-1/2)*(1-1/3)*(1-1/4)*...*(1-1/999)
(1/2+1).(1/3+1).(1/4+1)...(1/999+1)
p = (1-1/2) (1-1/3) (1-1/4) .......(1-1/999) (1-1/100)
