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Inverse functions

  1. Apr 2, 2007 #1
    how do i find
    f(x)^-1 of y=4x+9/2x-3
    the answer in the back of the text book is

    f(x)^-1=3x+9/2x-4
     
  2. jcsd
  3. Apr 2, 2007 #2
    Show your attempt at a solution, or pay me 1 dollar for doing your homework for you (your choice).
     
  4. Apr 2, 2007 #3
    2x=4x+9/y + 3y/y
    2x=4x+9+3y/y
    How do i move 4x to the other side?
     
  5. Apr 2, 2007 #4
    is 9/2x in your original post 9/(2x)? Just want to check.
     
  6. Apr 2, 2007 #5
    Heres the full working out:
    y(2x-3)=4x+9
    2x-3=4x+9/y
    2x=4x+9/y + 3
    2x=4x+9/y + 3y/y
     
  7. Apr 2, 2007 #6
    You gotta learn to put brackets in your eqns. There's no way anyone could have understood your original problem without the brackets.

    y(2x-3)=4x+9
    x(2y-4)-3y=9
    x=(9+3y)/(2y-4)
     
  8. Apr 2, 2007 #7
    Sorry to bother u again but how
    do u get from
    y(2x-3)=4x+9 to
    x(2y-4)-3y=9
     
  9. Apr 2, 2007 #8
    expand and collect terms in x

    y(2x-3)=4x+9
    ->
    y2x-3y=4x+9
    ->
    x(2y)-3y=x(4)+9
    ->
    x(2y-4)-3y=9
     
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