You are Here: Home >< Maths

# Confused about transformation questions watch

1. Describe a single transformation that would map the graph of y = x^2 + 2 onto the graph of y = 2x^2+ 4

I put stretch by scale factor 2 in y direction and 1/2 in x direction, but answers just say stretch by sf 2 in y direction.

I'm really confused by this... can someone explain it please? Thanks :/

(graphs and functions are really annoying me and I'm forcing myself to understand them)
2. so if f(x) is x2 + 2 then 2f(x) is 2( x2 + 2 )
3. (Original post by amaraub)
Describe a single transformation that would map the graph of y = x^2 + 2 onto the graph of y = 2x^2+ 4

I put stretch by scale factor 2 in y direction and 1/2 in x direction, but answers just say stretch by sf 2 in y direction.

I'm really confused by this... can someone explain it please? Thanks :/

(graphs and functions are really annoying me and I'm forcing myself to understand them)
Well if I stretch by s.f. 2 in the y direction and s.f. 1/2 in the x-dir I'd get
4. So for Describe a single transformation that would map the graph of y = x^2 + 2 onto the graph of y = x^2+4x+6

I put translated by vector [-4,6] but the answer says translation by 2 units in -ve x direction. Is it because it's x^2, so you put -2 in instead of -4? Mad confused lol
5. (Original post by amaraub)
So for Describe a single transformation that would map the graph of y = x^2 + 2 onto the graph of y = x^2+4x+6

I put translated by vector [-4,6] but the answer says translation by 2 units in -ve x direction. Is it because it's x^2, so you put -2 in instead of -4? Mad confused lol
which is a translation by -2 along the x-axis from
6. (Original post by the bear)
so if f(x) is x2 + 2 then 2f(x) is 2( x2 + 2 )
So when you stretch in the y direction you times everything by the sf?
7. (Original post by amaraub)
So when you stretch in the y direction you times everything by the sf?
The simple rule is that when you stretch in the y-dir by s.f. , you simply take and replace it by . Similarly if its along the x-axis. Just take and replace it by .

If it's a translation along the y-axis by , then you take and replace it by . Similarly for the x-axis.

Then all you need to do is just rearrange to get or whatever form they ask for.

EXAMPLE:

can be rewritten as which in turn gives which is clearly a translation by vector from the graph as you simply replace and
8. [QUOTE=RDKGames;74371654]The simple rule is that when you stretch in the y-dir by s.f. , you simply take and replace it by . Similarly if its along the x-axis. Just take and replace it by .

Ok, so if I was to enlarge y=x^2 + 2 by sf 2 in Y direction I would do y/2=x^2+2 which makes y= 2x^2 + 4?

And If I was to do enlarge by sf 2 in x direction I'd do y = (x/2)^2 + 2, which makes y = x^2 /4 +2?

(Original post by RDKGames)
EXAMPLE:

can be rewritten as which in turn gives which is clearly a translation by vector from the graph as you simply replace and
Ah ok. So since its x^2 + 2 -> x^2+4x+6 I would do

y = (x+2)^2 +2, so its a translation by [-2,0]?

Is that the main way to do it? Because for a harder question I would be a lot more difficult to see what to put into the bracket
9. (Original post by amaraub)

Ok, so if I was to enlarge y=x^2 + 2 by sf 2 in Y direction I would do y/2=x^2+2 which makes y= 2x^2 + 4?

And If I was to do enlarge by sf 2 in x direction I'd do y = (x/2)^2 + 2, which makes y = x^2 /4 +2?

Ah ok. So since its x^2 + 2 -> x^2+4x+6 I would do

y = (x+2)^2 +2, so its a translation by [-2,0]?

Is that the main way to do it? Because for a harder question I would be a lot more difficult to see what to put into the bracket
That's the main way to do it, and you can clearly see these match the answers in your book - they're all correct. If you find one you cannot do using these principles, post it here and we'll give you a hint.
10. (Original post by RDKGames)
That's the main way to do it, and you can clearly see these match the answers in your book - they're all correct. If you find one you cannot do using these principles, post it here and we'll give you a hint.
Ok thanks man A level maths is legit killing me
11. (Original post by RDKGames)
That's the main way to do it, and you can clearly see these match the answers in your book - they're all correct. If you find one you cannot do using these principles, post it here and we'll give you a hint.
If i was to enlarge (x+9)^3 + 2(x+9)^2 + 10 by a scale factor of 2 in the y direction would I do y/2 = (x+9)^3 + 2(x+9)^2 + 10, which gives me

2(x+9)^3 + 4(x+9)^2 + 20? I put it in desmos but it doesn't look right
12. (Original post by amaraub)
If i was to enlarge (x+9)^3 + 2(x+9)^2 + 10 by a scale factor of 2 in the y direction would I do y/2 = (x+9)^3 + 2(x+9)^2 + 10, which gives me

2(x+9)^3 + 4(x+9)^2 + 20? I put it in desmos but it doesn't look right
Why doesn't it look right?

It has been stretched parallel y-axis by s.f. 2. All the stationary points are twice as high up than they were before. Everything in the region gets stretched twice downwards. Everything is as expected.
14. (Original post by RDKGames)
Why doesn't it look right?

It has been stretched parallel y-axis by s.f. 2. All the stationary points are twice as high up than they were before. Everything in the region gets stretched twice downwards. Everything is as expected.
sh*tden thanks
15. (Original post by RedGiant)
yo i'm baffed with life. i'm not bad at maths you know but this graph stuff is confusing the hell out of me
16. (Original post by amaraub)
yo i'm baffed with life. i'm not bad at maths you know but this graph stuff is confusing the hell out of me
I can see m8, what exam board are you with?

17. (Original post by RDKGames)
Why doesn't it look right?

It has been stretched parallel y-axis by s.f. 2. All the stationary points are twice as high up than they were before. Everything in the region gets stretched twice downwards. Everything is as expected.
When reflecting in the y axis, do you times all the x by -1, and when reflecting in the x axis, do you times everything by -1?

(Original post by RedGiant)
I can see m8, what exam board are you with?

edexcel, u?

following so i can dm for maths and chat u up
18. (Original post by amaraub)
edexcel, u?

following so i can dm for maths and chat u up
I'm on edexcel as well (done chapters 1-7 but don't know which bit of the spec this is)
19. (Original post by amaraub)
When reflecting in the y axis, do you times all the x by -1, and when reflecting in the x axis, do you times everything by -1?
Same principles as above. Reflection in the y-axis means and reflection in the x-axis means .

Wasn't this covered in GCSE reflections of graphs or something...?
20. (Original post by RDKGames)
Same principles as above. Reflection in the y-axis means and reflection in the x-axis means .

Wasn't this covered in GCSE reflections of graphs or something...?
Yeah it probably was but I didn't really listen during GCSE lessons :/ Thanks though

(Original post by RedGiant)
I'm on edexcel as well (done chapters 1-7 but don't know which bit of the spec this is)
This is chapter 4. I have 2 teachers, and 1 of them is really good, but the other is a total d*ck and hates me. Unfortunately the d*ck is the one that covered chapter 4, but we barely did any exercises in the textbook, and now I'm trying to do all of them and the 2 tasks on maths genie and really try to understand each concept. I''ve never really listened with graphs as in my old school we did graphs in year 10 with some dead teacher so in year 11 we just skipped ahead with our new better teacher.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: November 1, 2017
Today on TSR

### University open days

• Southampton Solent University
Sun, 18 Nov '18
Wed, 21 Nov '18
• Buckinghamshire New University
Wed, 21 Nov '18
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams