Recent content by jav

  1. J

    Finite abelian group into sequence of subgroups

    G finite abelian group WTS: There exist sequence of subgroups {e} = Hr c ... c H1 c G such that Hi/Hi+1 is cyclic of prime order for all i. My original thought was to create Hi+1 by reducing the power of one of the generators of Hi by a prime p. Then the order of Hi/Hi+1 would be p, but...
  2. J

    Radius of Convergence Problem with Solution Attempt

    Check your an+1 term. The [(n+1)!] should be squared.
  3. J

    What are the cardinality problems in set theory and how can they be solved?

    I have been studying set theory, and come across a few problems that I have not been able to solve. I am trying to prove the bijections exist. Let N = Set of all natural numbers Let BA = Set of all functions from A to B 1) Prove |NN x NN| = |NN| 2) Prove |(NN)N| = |NN| Any explanation into...
  4. J

    Complex numbers, basic problem

    Homework Statement Know: modulus(z) < 3 WTS: |Im(z2 - zbar + 6)| <12 where zbar is the complex conjugate Homework Equations z = x + iy The Attempt at a Solution |Im(z2 - zbar + 6)| = |Im(x2 + 2i*x*y - y2 - x + iy + 6)| = |2xy + y| So I want to show |2xy + y|< 12 I already proved it...
  5. J

    Need help finding graduate analysis book

    I have just taken real analysis I and II (single and multivariable respectively) as an undergrad. I am planning on taking the grad analysis course next year. From what I gather Rudin seems to be the time-tested bible of analysis, but I don't know at what level the book is written. Can...
  6. J

    Finding Power Series Representation of Derivatives: 1/x-9

    This expression can be written as -1/9 * d/dx (1/(1-x/9)). Then think geometric series. Can you see it from there?
  7. J

    Volume Generated by Hyperboloid & Plane

    It looks like you are integrating z^2 instead of z. Also shouldn't there be an extra r in the integral? ie. \int\int z*r dr d\vartheta whereas it looks like you are doing \int\int z^2 dr d\vartheta
  8. J

    Proving the Convergence of the Sequence n^(1/n)

    Ah of course, thanks.
  9. J

    Proving the Convergence of the Sequence n^(1/n)

    Sorry, I was out all weekend, but I should have given what I started with. I took the natural log, and used l'hospital's rule, but I ran into a problem when I was trying to prove that lim(ln(an)) = A -> ln(lim(an)) = A ie. continuity. Clearly, it is true and the function is continuous, but I...
  10. J

    Proving the Convergence of the Sequence n^(1/n)

    I know lim n^(1/n) = 1 n->infininity Does anyone have ideas on how to prove this? I feel like its something simple I am missing. Thanks
  11. J

    Solving Integration Problem: I Have No Idea What I'm Doing Wrong

    This is true if the function is even. Try not using this when you solve for the integral. ie. use 1 and 3 as your new bounds for your u integral
  12. J

    What is the Expansion of X^n + Y^n When n is Even?

    Try alternating signs, and it becomes straightforward.
  13. J

    Probability function of a discrete random variable problem

    In this case, you are trying to solve for the probability that card X is an ace (without knowing any of the other cards). If you solve for the P(a|b) you are solving for the probability of event a occurring given that you know b has occurred. ie you want to solve for P(X is an ace and...
  14. J

    Worked out examples using Cauchy criterion for series

    Think he means groups of (1/2)^n terms ie 1 + 1/2 + (1/3 + 1/4) + (1/5 + 1/6 + 1/7 + 1/8) + (1/9 + ...+ 1/16) + (1/17+...+ 1/32) ... > 1 + 1/2 + (1/4 + 1/4) + (1/8 + 1/8 + 1/8 + 1/8) + (1/16 + ...+ 1/16) + (1/32+...+ 1/32) ... And note that s2n-1 = n+1 for the second sequence of...
  15. J

    Meaning of Independent Identically distributed random variables

    If they have the same pdf, then they by definition have the same mean and variance.
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