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Core 2- Differentiation and Fractional Indices

Could anyone help me in part b of the question, in part a I got dy/dx= 45/2 x^1/2 - 5/2 x^3/2. In part b I get that you have to make dy/dx = 0, but don't know how to rearrange to fin x. It would be much appreciated if anyone could help me.

ImageUploadedByStudent Room1399394132.168823.jpg


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Original post by Jimmy20002012
Could anyone help me in part b of the question, in part a I got dy/dx= 45/2 x^1/2 - 5/2 x^3/2. In part b I get that you have to make dy/dx = 0, but don't know how to rearrange to fin x. It would be much appreciated if anyone could help me.

ImageUploadedByStudent Room1399394132.168823.jpg


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How about multiplying by x^1/2?
Original post by alexmufc1995
How about multiplying by x^1/2?


Would you be able to give me a full worked out solution, so I know what I am doing next time, I will probably learn better like that,my thanks


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Original post by Jimmy20002012
Would you be able to give me a full worked out solution, so I know what I am doing next time, I will probably learn better like that,my thanks


Surely there are examples in your text book/notes that solve similar problems - so use those full solutions to inform your understanding of this question
Original post by TenOfThem
Surely there are examples in your text book/notes that solve similar problems - so use those full solutions to inform your understanding of this question


I don't have any :frown:


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Reply 5
Original post by Jimmy20002012
Could anyone help me in part b of the question, in part a I got dy/dx= 45/2 x^1/2 - 5/2 x^3/2. In part b I get that you have to make dy/dx = 0, but don't know how to rearrange to fin x. It would be much appreciated if anyone could help me.

ImageUploadedByStudent Room1399394132.168823.jpg


Posted from TSR Mobile


You can take out a factor of (5/2)x1/2(5/2)x^{1/2} which will help you find where dy/dx = 0
Original post by Jimmy20002012
I don't have any :frown:


You don't have any notes or textbook?

Here is an example

2x12+5x52=2x+5x2x=x(2+5x2)2x^{\frac{1}{2}} + 5x^{\frac{5}{2}} = 2\sqrt{x} + 5x^2\sqrt{x} = \sqrt{x}(2 + 5x^2)
This is just confusing, can't seem to understand


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Original post by Jimmy20002012
This is just confusing, can't seem to understand



What was confusing
Do you know about fractional indices
Do you understand how to factorise
Reply 9
Original post by Jimmy20002012
This is just confusing, can't seem to understand


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Can you see how to take a factor of 52x1/2\dfrac{5}{2}x^{1/2} out of the expression you've obtained for dydx\dfrac{dy}{dx}?

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