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Homework Help: Silly me: Not thinking straight today: simple questions

  1. Feb 18, 2008 #1
    1. The problem statement, all variables and given/known data
    Two equations here, I need to simplify both of them but I'm not too sure:
    (y^2+1)/(y^2+1) as well as (t^2-s^2)/(s+t)^2

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 18, 2008 #2
    If you typed in the first one correctly then it should just simplify to 1 if the same equation divided by itself. The second one just factor the top and you should see the answer.
  4. Feb 18, 2008 #3
    I hope you take a look at the first one again, if you typed it right. It looks like

    [tex]\frac{y^2 + 1}{y^2 + 1}[/tex]

    For the second one, think how you would factor the numerator. Is it special in any way?
  5. Feb 18, 2008 #4
    Oops, sorry, first one is y^2+1/y^2-1 .... But I don't quite get what You mean on the second one. Sorry, I realize these are probably cereal box games to you but today is not my day for thinking... I've been out of it.
  6. Feb 18, 2008 #5
    I got the second one to: t^2-s^2 / t^2+s^2 .... But the back of the book says its going to be t-s/t+s ...

    For the first question, it says you cannot simplify further than what it's already at.
  7. Feb 18, 2008 #6
    I do not know of any simple way to simplify

    [tex]\frac{y^2 + 1}{y^2 - 1}[/tex]

    For your other problem however, don't run away from it. We are telling you that there is a way to factor the numerator. It is a common factorization that you need to get used to, so look again in your book or your study aid or try to think about an answer.

    EDIT: Yes, the book is right; there isn't anyway to simplify the first one. That's because all the simplifications you are doing rely on factorization and then canceling factors in the resulting fraction. There is no way to factor [itex]y^2 + 1[/itex] and have it cancel out with a factor of [itex]y^2 - 1[/itex]. However, it is possible to factor [itex]t^2 - s^2[/itex]. Figure out how, and you will have solved your problem.
    Last edited: Feb 18, 2008
  8. Feb 18, 2008 #7
    (s+t)^2 is not t^2+s^2 remember the that (s+t)^2 is (s+t)(s+t), but if you factor the top you do not have to expand the bottom.
  9. Feb 18, 2008 #8
    OHH! I see how to factor the top. -1(s^2+t^2) . then... then it just equals -1?

    EDIT: Wait, No, I see the error in that... Still not getting is :S
  10. Feb 18, 2008 #9
    I think what's confusing me is knowing that the answer has to have both the exponents come out of the equation, and I don't see how they do that without dividing the top and bottom which... you can't do.
  11. Feb 19, 2008 #10
    Try multiplying (a - b) with (a + b)
  12. Feb 19, 2008 #11
    see, that solved it. Thanks. I was doing (a-b)^2 = (a-b)(a-b)
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