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# Further Maths rates of change and second differentiation Watch

1. No sure how about to start this. Help!
2. Lay out the information.

Sub into and differentiate it with respect to r. Make it equal 0 and solve for r. Check this gives the minimum and plugging it through the second differential.
3. if your not going to be helpful jog on or do you not have a life
4. (Original post by forxer)
if your not going to be helpful jog on or do you not have a life
But you literally posted the same thing on the other thread, no need for a duplicate.
5. (Original post by RDKGames)
Lay out the information.

Sub into and differentiate it with respect to r. Make it equal 0 and solve for r. Check this gives the minimum and plugging it through the second differential.
so i got r as 1/300pi for the first differentiate
6. (Original post by forxer)
if your not going to be helpful jog on or do you not have a life
That is very helpful for everyone else, it avoids duplication of efforts
7. (Original post by SeanFM)
That is very helpful for everyone else, it avoids duplication of efforts
8. (Original post by forxer)
so i got r as 1/300pi for the first differentiate
Show your working if you get stuck.

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