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Homework Help: Algebra with a little differenentation

  1. May 30, 2012 #1
    I have the following terms
    X, Y, Z, J and K
    Where everything is a function of t

    I want to combine these equations into a single equation where the X, Y, and Z terms are no longer in the equation and there are only terms of J on the RHS and K on the LHS or visa versa

    i) X = Y^2 + Y
    ii) Z = dX/dt
    iii) J = Z + Y
    iv) K = X + J

    I'm told this should be possible but not matter which way I combine these I get something along the lines of

    K = J^2 + ( K'(t) + J'(t) )^2 - 2*J ( K'(t) + J'(t) ) - ( K'(t)+J'(t) )

    and obviously this is going to leave you with products of J and Ks that can't be seperated (I need all the K'(t) terms to be over with it's buddy on the LHS). No matter what stratagy I use to avoid this I can't help but get these terms combining.
  2. jcsd
  3. May 30, 2012 #2
    Where did this problem arise?

    Who told you this is possible?
  4. May 30, 2012 #3
    It's a simplification of an RCR electrical circiut problem with a variable resistor that varies as a function of the current. It was an assignment. I've asked and I know the first part is correct.
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