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Homework Help: Why cant I do this? (Regarding finding domain of function)

  1. Sep 11, 2012 #1
    Last edited by a moderator: Sep 11, 2012
  2. jcsd
  3. Sep 11, 2012 #2
    -4x +4 is not x

    Also be careful with the direction your inequality sign is supposed to point if you start dividing by negatives.
  4. Sep 11, 2012 #3


    Staff: Mentor

    In addition to what aftershock said, you are missing something else. For f(x) to be defined, it must be true that 9 - 4x ≥ 0 AND 2x - 1 > 0. The domain for this function will be all of the numbers that satisfy both inequalities.

    Also, you have a mistake in this work, similar to the one that aftershock pointed out.
    2x - 1 > 0
    2x > 1 (OK, so far)
    Then you subtract 2 from both sides. What's wrong with that is that 2x - 2 ≠ x. To isolate x, divide both sides by 2.
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