test 3 review

3 Responses to test 3 review

1. Javier says:

   May 4, 2016 at 7:31 pm

   Hi,
   I believe there is a misunderstanding here. Your problem is a finite sequence hence is not our so called “friend” (more like an enemy). Anyhow, I believe your should be G(x)= (1-(4z)^5)/(1-4z) Why? well, set what G(x) is equals to your sequence {1+4z+16z^2+64z^3+256z^4} then you can see that multiplying the sequence with (1-4z) it will leave a 1-1024z^5 (1-(4z)^5) term on the right side. Therefore, you can see why y G(x) works since (1-(4z)^5)=(1-(4z)^5) after you distribute and the rest of the terms cancel. 1 is not equals to (1-(4z)^5). If you or anyone else thinks I am wrong, please let me know before Sunday 2359.

   Reply
2. Bryan Tinjaca says:

   May 6, 2016 at 2:38 pm

   Following Example 2 on pg 537 in the book I got the following
   1,4,16,64,256
   (1+4z+16z+64z+256z)
   1+4z+(4z)^2+(4z)^3+(4z)^4
   so Javier I believe you have the right answer only signs are switched
   (4z^5 -1)/(4z-1) =1+4z+(4z)^2+(4z)^3+(4z)^4

   Reply
3. Kate Poirier says:

   May 11, 2016 at 1:54 pm

   Hi guys, I haven’t checked your work carefully, but it does seem like Javier and Bryan were on the right track. You can always check your answer by multiplying.

   Also, I’d say that, since finite sequences have generating functions that are *polynomials* finite sequences are verrrrry friendly! Not enemies! But they certainly are different from the one friend we like the most 😉

   Reply