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# C2

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1. https://a44694f152ee562e38a9454969d2...%20Edexcel.pdf

help with question 7a because why not?

Edit: Actually i need help with part b
2. It should be clear that the total length of the 12 edges is where y is the dimension of the cuboid that you aren't given.

But you know that the volume is 81, so . Therefore , as required.

EDIT: Not sure why part (b) should cause any problems. It's your typical differentiate, set equal to 0, solve, question.
3. (Original post by IrrationalRoot)
It should be clear that the total length of the 12 edges is where y is the dimension of the cuboid that you aren't given.

But you know that the volume is 81, so . Therefore , as required.
Thanks for that what about part b then?
4. (Original post by thefatone)
Thanks for that what about part b then?
You have an expression for in terms of , differentiate and set it equal to 0 to find the minimum points.
5. (Original post by Zacken)
You have an expression for in terms of , differentiate and set it equal to 0 to find the minimum points.
derp, thanks so much, i'm forgetting everything, although things are coming back slowly to me ^-^
6. (Original post by thefatone)
derp, thanks so much, i'm forgetting everything, although things are coming back slowly to me ^-^
No problem.
7. (Original post by Zacken)
No problem.

then

i don't need to put a do i?
8. (Original post by thefatone)

then

i don't need to put a do i?
No, is injective for odd . i.e: you only use the when you have x^(even number)
9. (Original post by Zacken)
No, is injective for odd . i.e: you only use the when you have x^(even number)
i though so thanks
10. (Original post by thefatone)

then

i don't need to put a do i?
Do you mean x=3?
11. (Original post by thefatone)
i though so thanks
Awesome.
12. (Original post by Math12345)
Do you mean x=3?
uh oh
i put in into my calculator thanks

(Original post by Zacken)
Awesome.

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