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# Help with Optimisation question? watch

1. So far I've differentiated the equation in part (c) and got -32*pi*r^-2 + 4*pi*r. Not sure what I do next?

My answer for part (a) was h = 16/(r^2) if that helps.

Thanks
2. (Original post by ℓove)

So far I've differentiated the equation in part (c) and got -32*pi*r^-2 + 4*pi*r. Not sure what I do next?

My answer for part (a) was h = 16/(r^2) if that helps.

Thanks
Set dA/dr=0.
3. (Original post by ℓove)

So far I've differentiated the equation in part (c) and got -32*pi*r^-2 + 4*pi*r. Not sure what I do next?

My answer for part (a) was h = 16/(r^2) if that helps.

Thanks
Looks right. Now set it equal to 0 and find the value of r that will minimise the area.
4. Thanks got it, 24 pi

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