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Stretch a shape in a given direction by a scale factor watch

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    I have a triangle with the points,
    O(0,0)
    A(0,5)
    B(2,2)

    I have a few questions like this:
    Stretch, scale factor 5, parallel to Ox

    I'm not quite sure what this means. It's in the 'before you start' section of this topic, so I guess it's from GCSE, but I really don't remember coming across it before.

    Thanks.


    EDIT- and also there is a question on using function notation.

    If f(x)=x^2, find the value of

    a. f(3)
    b.f(3)+2
    etc... I can do all of them

    But then it tells me to write an expression for f(2x).
    This, I don't understand.


    EDIT again-
    If f(x)=x^2, find the value of 3f(3).
    The answer I got was 27. However in the answer book it says 27, 4x^2.
    I assumed that meant 27 or 4x^2, is this right?
    I've had a look at it and don't understand where the 4x^2 comes from.
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    It means that the shape is stretched parallel to the x-axis. The "scale factor 5" bit means that, say, the point (1,0) is now at (5,0). Since the stretch is parallel to the x-axis, the y-coordinate is unaffected.
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    If you're asked to stretch parallel to 0x then you want to multiply all of your x-cooridinates by the scale factor.

    Secondly, if you have f(x) = x^2
    then, f(2) = (2)^2, you basically replace any x by the number in the function brackets.

    So, f(2x) = (2x)^2 = 4x^2
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    (Original post by tgodkin)
    If you're asked to stretch parallel to 0x then you want to multiply all of your x-cooridinates by the scale factor.

    Secondly, if you have f(x) = x^2
    then, f(2) = (2)^2, you basically replace any x by the number in the function brackets.

    So, f(2x) = (2x)^2 = 4x^2
    And if it says stretch parallel to 0y, it means multiply all the y coordinates to the scale factor, right.
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    Thats right.
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    (Original post by Kash:))
    I have a triangle with the points,
    O(0,0)
    A(0,5)
    B(2,2)

    I have a few questions like this:
    Stretch, scale factor 5, parallel to Ox.
    Can I just check,

    the new coordinates would be
    O(0,0)
    A(0,5)
    B(10,2)
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    (Original post by Kash:))
    EDIT again-
    If f(x)=x^2, find the value of 3f(3).
    The answer I got was 27. However in the answer book it says 27, 4x^2.
    I assumed that meant 27 or 4x^2, is this right?
    I've had a look at it and don't understand where the 4x^2 comes from.
    4x^2 is f(2x)
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    (Original post by Kash:))
    Can I just check,

    the new coordinates would be
    O(0,0)
    A(0,5)
    B(10,2)
    Thats right.
 
 
 
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