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Homework Help: Functions: Input of a function is another function.

  1. Mar 11, 2012 #1
    The input for a function can be another function. If h(x) = 2x - 5, determine a simplified expression for each of the following.

    a) h(4x) b) h(2x+3) h(x/2-1)

    h(x) = 2x - 5

    For a) h(4x) it can be h(4x) = (4)2x - 5 = 8x -5 however I am not sure why the 4 was not applied to the -5 also.

    I am not sure how to solve this problem. If anyone could give me a link to a website that explains it and gives a proof for it, I would appreciate that act very much.
    Last edited: Mar 11, 2012
  2. jcsd
  3. Mar 11, 2012 #2


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    Homework Helper

    Look up function composition for details.

    The basic ideas is that the argument of your function is evaluated at the new function, that means replace the x of f(x) as they appear in the definition of your f(x) with the other function g(x) or f(g(x)).
  4. Mar 13, 2012 #3
    Thank you Pyrrhus

    I looked it up some more and it clicked.

    I do not know how to close a thread.
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