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Find the first derivative

  1. Sep 2, 2006 #1
    I've got f(x)=x^2-(7x^2)/2-9x+3

    I need to find the first derivative of it but I get as far as 2x- but I'm stumped as to what to do with (7x^2)/2 Would I use the quotiant rule? Or should I somehow bring the 2 up to the top and if so how do I do that?
  2. jcsd
  3. Sep 2, 2006 #2
    If you mean [tex]f(x) = x^2 + \frac {7x^2}{2} -9x + 3[/tex], I'm sure that you can see what the answer will be.

    If on the other hand you mean [tex]f(x) = x^2 + \frac {7x^2}{2 - 9x} + 3[/tex], use quotient rule.
  4. Sep 2, 2006 #3
    I guess I risk coming off really stupid but I do mean the first one (7x^2)/2 It looks so simple I know, but i'm not sure which direction to go with the 2. Sorry if I'm wasting your guys' time or anything, but I can't see what the answer should be.
  5. Sep 2, 2006 #4
    treat 7/2 as a constant (which it is :)) and get the derivative of x^2
  6. Sep 2, 2006 #5
    Oh! Thank you! Funny how the simplest things can seem so hard. I feel silly now.
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