1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Did I get it wrong? (transformation problem)

  1. Jan 22, 2007 #1
    1. The problem statement, all variables and given/known data

    I just got back from writing my grade 12 math final and I figure I did really well. There was only one question that stumped me, and it was freaking stupid, too. So the problem was this:

    There was a picture of [tex]y=x^{3}[/tex] and the points P(2,8) was labelled. The question was where does the point P go if the graph is expanded horizontally by a factor of 3 about the line x=4... What the hell did they mean? I thought they meant that you first shift the graph over 4 places to x=4 and then you would apply the transformation, the point would end up being Q(10,8) but that wasn't even on there.

    Here were my choices...

    A.(8,8)
    B.(14/3,8) (I think)
    C.(10/3,8)
    D.(-2,8)

    I ruled out D pretty quickly and went with A... but it didn't make any sense. Did I get it wrong? :cry:

    Pretty sad the the only question that stumped me was a transformation question... :eek:

    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: Jan 22, 2007
  2. jcsd
  3. Jan 22, 2007 #2
    Woops, I meant you would apply the transformation and then shift it over, wrong way around. But anyways, both methods were fruitless.
     
  4. Jan 23, 2007 #3

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    I would interpret that to mean that the point's distance from x= 4 is multiplied by 3- if x is larger than 4, then it moves to the right 3 times that distance. If x is less than 4, then it moves to the left 3 times that distance.

    In this example, 2< 4 and the distance from 2 to 4 is 4-2= 2. (2, 8) is transformed to a point with x< 4 and 4- x= 3(2)= 6 so x= 4- 6= -2. Since the change is only horizontal, y does not change.
    (2, 8) is transformed to (-2, 8)

    How did you rule out D "pretty quickly"?
     
  5. Jan 23, 2007 #4
    That sounds like a good interpretation. Definitely makes sense to me now that I think about it. I figured that no positive stretch is going to result in a positive point moving to the left... But I was wrong!

    Thankyou for clearing that up, I understand the concept now.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Did I get it wrong? (transformation problem)
Loading...