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# OCR Core 3 watch

1. In the OCR core 3 exam.

For a question like (3x+4)^5

Would you have to show all working out with the u-substitution or can you do the short way of the power times the differential of the bracket times the bracket with a reduced power?

Will you lose marks by using the short method?
2. You can just write down the answer for something as simple as that.
3. i would just do y=(3x+4)^5

=> dy/dx= 15(3x+4)^4

As you can work it out in your head (without to much thought) you don't need to write it all out. If there are lots of substitutions or more complex functions id write it all out just to make sure i get it right.
4. Can I use the total marks as some form of indication as to whether I have to show all working then?

e.g. if it is over 4 marks I should do it in full?
5. (Original post by kkid106)
Can I use the total marks as some form of indication as to whether I have to show all working then?

e.g. if it is over 4 marks I should do it in full?

You ONLY have to show necessary working , provided that your method is clear.
6. (Original post by steve2005)
You ONLY have to show necessary working , provided that your method is clear.
But how is necessary defined?
7. (Original post by kkid106)
Can I use the total marks as some form of indication as to whether I have to show all working then?

e.g. if it is over 4 marks I should do it in full?
If the question specifies a particular method then you must use that method. Otherwise it is entirely up to you.
8. (Original post by kkid106)
But how is necessary defined?

Just work out the problem. Remember that the examiner is more experienced than you and will be familiar with the answer, DON'T employ magic, don't work out the answer on the desktop or on plotting paper.

An honest answer is all that is necessary.

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Updated: December 31, 2012
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