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# Higher Maths differentiation help watch

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1. Im looking for the workings to the following differentiation question from Heinemann Higher Maths page 113 question 7a. if anyone has it

It involves a diagram so I can't post the question.
2. Use this to do the diagram and then I'm sure someone will be able to help you.
3. I have attached a diagram of the question

I hoep someone can help
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4. (Original post by jjlang)
I have attached a diagram of the question

I hoep someone can help
its just 2x*(3-x^2)
5. The notation is probably what is confusing you because you can easily get the x and X in the diagram mixed up and try to over think it.

It would be easier to say "PQ = 2t metres" and you're wanting to show the area is in size.

The length of PQ is 2t, and it is symmetric about the y axis, so the point q has an X value of t (if you were using the questions notation it would be X=x, which is just confusing!).
Anyway, at q X=t. But q is also on the line , so put in X=t to get the Y coordinate of q which is .

Now I know the height of the rectangle, which is metres, and I know it is 2t metres long. Area is just the product of height and length so you have .

Now you can convert back into the stupid notation of the question by turning t's into x's to get .

It is a bit of a nasty question in how it is setup.
6. Cheers for the reply mate

Its seems a bit of a lot of work for a differentiation question and I haven't seen anything that hard in the past papers.

I'm just glad I have the answer now.

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