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

1. 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.
2. 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.
3. 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
4. (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.
5. Thats right.
6. (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)
7. (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)
8. (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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