Turn on thread page Beta
 You are Here: Home >< Maths

# curve sketching watch

1. Please explain how to sketch the graph of y=ln(2x-3). Thanks.
2. (Original post by Sister Clo)
Please explain how to sketch the graph of y=ln(2x-3). Thanks.
Start by looking at the equations

y=ln(x)
y=ln(2x-3)

What transformation/s turn ln(x) into ln(2x-3)

Then apply these to the graph

It's also a good idea to sub in y=0 or x=0 and solve for x or y respectively to find some intercepts to guide you
3. (Original post by Sister Clo)
Please explain how to sketch the graph of y=ln(2x-3). Thanks.
Consider what transformations take place when you go from (which I hope you know how to draw) to . Then consider how it would look like after these transformations, keeping in mind the critical points.
4. (Original post by RDKGames)
Consider what transformations take place when you go from (which I hope you know how to draw) to . Then consider how it would look like after these transformations, keeping in mind the critical points.
Thanks. I transform by 2x (stretch in the x direction, so half the x-values), then translate 3 to the right. Doesnt seem to be the same when using a grapher.
5. (Original post by Sister Clo)
Thanks. I transform by 2x (stretch in the y direction), then translate 3 to the right. Doesnt seem to be the same when using a grapher.
Why the y-direction? You're applying these onto , not . If it were the latter than it would be true, however alternatively it is also a stretch by s.f. 1/2 in x-direction.

Before that happens though, I recommend you translate it by 3 to the right because is a translation to the right by 3 units, and then is a stretch by s.f. 1/2 along the x-axis.
6. (Original post by AHappyStudent)
Start by looking at the equations

y=ln(x)
y=ln(2x-3)

What transformation/s turn ln(x) into ln(2x-3)

Then apply these to the graph

It's also a good idea to sub in y=0 or x=0 and solve for x or y respectively to find some intercepts to guide you
Thanks - I stretch in the x-direction by scale factor half then translate 3 to the right. Seems to be different using graph plotter
7. (Original post by RDKGames)
Why the y-direction? You're applying these onto , not . If it were the latter than it would be true, however alternatively it is also a stretch by s.f. 1/2 in x-direction.

Before that happens though, I recommend you translate it by 3 to the right because is a translation to the right by 3 units, and then is a stretch by s.f. 1/2 along the x-axis.
Thanks yet again - I think the issue I have problem getting my head around is why translate first, when I would do the 2x first for all other graphs without a problem.
8. (Original post by Sister Clo)
Thanks yet again - I think the issue I have problem getting my head around is why translate first, when I would do the 2x first for all other graphs without a problem.
You can do stretch first, just depends on the preference. You apply transformations to , so if you do stretch by s.f. 1/2 first you end up with and now you need to translate by an appropriate such that is equal to - clearly here like it could be in the first scenario.
9. (Original post by RDKGames)
You can do stretch first, just depends on the preference. You apply transformations to , so if you do stretch by s.f. 1/2 first you end up with and now you need to translate by an appropriate such that is equal to - clearly here like it could be in the first scenario.

Thank you. Much appreciated.

Reply
Submit reply
Turn on thread page Beta

### Related university courses

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: October 8, 2017
Today on TSR

### A-Level OCR Biology Exam Discussion

Find out how you've done here

### 2,687

students online now

Exam discussions

Poll
Useful resources

## Make your revision easier

### 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

Can you help? Study help unanswered threads

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.