# Thread: Use of 4U techniques in Extension 1 Paper

1. ## Use of 4U techniques in Extension 1 Paper

Firstly, I'm sorry if this has been asked before or if this is not the right place for this question but I couldn't find the answer anywhere. My question is wether or not extension 2 students are allowed to use extension 2 techniques in the extension 1 HSC paper? For example, when calculating volume of a solid of revolution which is rotated about the y-axis, can I just use cylindrical shells instead of dealing with changing the dy -> dx method that is learned in extension 1? Thanks in advance!

2. ## Re: Use of 4U techniques in Extension 1 Paper

You should be abled to iirc. Like implicit differentiatin for rates is allowed so it should work

3. ## Re: Use of 4U techniques in Extension 1 Paper

You probably(?) won't be penalised for it as long as you show what you're doing, but typically you should never need to use 4U methods in 3U exams, or 3U methods in 2U exams etc. These methods are often slower or more tedious - and the exams are designed that way so as to not give any unfair advantages.

For example, in many problems involving volumes by revolution around the y-axis, the given equation might be a function whose inverse is much easier to integrate, e.g. $\log x$ or $\sin^{-1} x$.

4. ## Re: Use of 4U techniques in Extension 1 Paper

I have been told to never 4u techniques for a 3u question.
If you do it all correctly and get the right answer, they will give you the marks.
However, if you make a mistake and get some part of it wrong (even if it was that you missed a coefficient in your integral), you wont be awarded any marks as the methods you have used are outside the syllabus of 3u.
So better to be safe and stick with 3u techniques.

Thats what I have been told by my teacher.

5. ## Re: Use of 4U techniques in Extension 1 Paper

The questions will typically be designed such that 4u methods won't be needed to answer the question anyway (at least not needed to answer it more efficiently).

6. ## Re: Use of 4U techniques in Extension 1 Paper

We have personally been told that the methods of that course are of course favored, and majority of the time easier also. However, we have been taught that any knowledge from 4U can be applied in 3U, etc.

Interested to see if this is true?

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