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C3 help

Find all possible turning points and determine their nature

f(x)=x-lnx

I'm not too sure on differentiating this

Would I get: f ' (x) =1-1/x

and then make f ' (x) = 0 ?
(edited 9 years ago)
Original post by Incubator
Find all possible turning points and determine their nature

f(x)=x-lnx

I'm not too sure on differentiating this

Would I get: f ' (x) =1-1/x

and then make f ' (x) = 0 ?

your f ' (x) is correct. and you are right you make your f ' (x) = 0 then re arrange and you will also need f '' (x) for determining the nature.
Reply 2
Original post by crayolaguy
your f ' (x) is correct. and you are right you make your f ' (x) = 0 then re arrange and you will also need f '' (x) for determining the nature.




Thank you :smile:, I forgot my C1 stuff
Original post by Incubator
Thank you :smile:, I forgot my C1 stuff

Yeah I always forget core 1 stuff too..

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