c1 solomon paper D

Bit stuck on 8c in on paper D solomon c1

I am just getting a little confused what to do when they state y = f(1/2x)

The whole question

f(x) = 2x^2 + 3x -2

a) Solve equation f(x) = o DONE

b) Sketch the curve with equation y = f(x) Done

c/ Find the coordinates of the points where the curve with equation y = f(1/2x) crosses the coordinates.

I am just not sure what to do here - do I change the original f(x) by the scale factor of 1/2 and plot that graph? when I do this it doesnt give me the right answer.

I am geting a little confused with these types of questions.

I got stuck on a similar questions earlier :-(

Reply 1

SelfishWeiner

1

for f(ax) graphs, you change the x values by a scale-factor of 1/a.
Since a is 1/2, the scale factor is 2 - i.e. you double the x-coordinates of the points :smile:

Reply 2

Zacken

22

Original post by christinajane

Bit stuck on 8c in on paper D solomon c1

I am just getting a little confused what to do when they state y = f(1/2x)

The whole question

f(x) = 2x^2 + 3x -2

a) Solve equation f(x) = o DONE

b) Sketch the curve with equation y = f(x) Done

c/ Find the coordinates of the points where the curve with equation y = f(1/2x) crosses the coordinates.

I am just not sure what to do here - do I change the original f(x) by the scale factor of 1/2 and plot that graph? when I do this it doesnt give me the right answer.

I am geting a little confused with these types of questions.

I got stuck on a similar questions earlier :-(

What it means is just, wherever 'x' occurs in your original expression, replace it with an 'x/2'.

So f(x/2) = 2(x/2)^2 + 3(x/2) - 2.

But, really, all you need to do is notice that the curve crosses the coordinate axes precisely when x=0 so f(0).

And it crosses the other axes at double the value of the cross of f(x).

i.e: if f(x) crossed the x-axis at x=2 that is f(2) = 0. Then f(x/2) will cross the axis when x/2 = 2, that is, when x=4.

Which makes sense, since if you plug x=4 into f(x/2) you get f(4/2) = f(2) which is where f(2)=0. Obviously, it's not 4 - but I'm just using that as an example.

Reply 3

christinajane

OP

4

Ooo sorry zacken I am still a little unsure - done the first bit just so I could understand what I was doing...
e.g.

2(1/2)^2 + 3(1/2) - 2 = 0

Just not sure now.... Im sorry not at my best today!

Reply 4

christinajane

OP

4

I got the right numbers using your method but I just don't get it

so I got x = -4 and x = 1

but given tnis type of question again I wouldnt get it....

Reply 5

christinajane

OP

4

I figured it - Im a bit duh today

Reply 6

Zacken

22

Original post by christinajane

I figured it - Im a bit duh today

Well done!! :woo:

Reply 7

christinajane

OP

4

Basically that was just a question about transforming that original graph by f(1/2x)

I can do them usually - I think the way they worded the question threw me....

c1 solomon paper D

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