View Full Version : Reccurance relations
 
 Eelarch
Aug 23, 2009, 05:47 AM
Two sequences are generated by the recurrence relations Un+1=Aun+10 and 
Vn+1=2Avn + 6
 
the sequences approach the same limit as n --> infinity
 
determine the value of a and evaluate the limit
 
So far I have got L=6/1-(A/2)
 
L=8?
 galactus
Aug 23, 2009, 06:06 AM
Is this what you have?:
 
u_{n+1}=Au_{n}+10
 
v_{n+1}=2Av_{n}+6
 
 
If so, since they approach the same limit, we have L=AL+10
 
and L=2AL+6
 
Solve the system? 
 
I do not get 8.
 Eelarch
Aug 23, 2009, 06:43 AM
Would you then sue a simultanius equation to get the answer?
 
L=AL+10
L=2AL+6
 
A=4?
 
but if that's so then it wouldn't work because if there's a limit then -1<A<1
 galactus
Aug 23, 2009, 07:02 AM
If we solve L=AL+10 for L, we get L=\frac{10}{1-A}
 
Sub into the second one:
 
\frac{10}{1-A}=2A(\frac{10}{1-A})+6
 
A=\frac{2}{7}
 
and L=14