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Differentiation question

Q & working https://imgur.com/a/8Sq4BOm

Hi, this question involves finding the partial derivative with respect to p1. I know my answer seems a bit off but can't really detect any errors. This question restricts me to use only the normal calculation who doesn't allow checking to be done. IS there a way to spot the mistake in this case? I still don't know where it went wrong. Thanks

M, p1 & p2 are all positive constants
(edited 5 years ago)
Original post by coconut64
Q & working https://imgur.com/a/8Sq4BOm

Hi, this question involves finding the partial derivative with respect to p1. I know my answer seems a bit off but can't really detect any errors. This question restricts me to use only the normal calculation who doesn't allow checking to be done. IS there a way to spot the mistake in this case? I still don't know where it went wrong. Thanks

M, p1 & p2 are all positive constants


Didnt check all of it, but immediately noticed your V partial derivative is wrong.

[(P1 + P2)^-1] = -(P1+P2)^-2
since the partial derivative of the inside bracket is just 1 (you hold P2 constant hence it disappears)
Reply 2
Original post by RDKGames
Didnt check all of it, but immediately noticed your V partial derivative is wrong.

[(P1 + P2)^-1] = -(P1+P2)^-2
since the partial derivative of the inside bracket is just 1 (you hold P2 constant hence it disappears)

Oh, I see! Corrected that part now, and now everything seems to fall into place. I think I was asking you for help already back then for c3 & c4? Appreciate that. Anyways, for these differentitation, why can you be 100% certain whether your answer is right if you don't have the differentiation function in your calculator? Thank you
Original post by coconut64
Anyways, for these differentitation, why can you be 100% certain whether your answer is right if you don't have the differentiation function in your calculator? Thank you


Wolfram seems capable of dealing with it:

https://www.wolframalpha.com/input/?i=partial+derivative+m*p2+%2F(p1*(p1%2Bp2))+wrt+p1
Original post by coconut64
Oh, I see! Corrected that part now, and now everything seems to fall into place. I think I was asking you for help already back then for c3 & c4? Appreciate that. Anyways, for these differentitation, why can you be 100% certain whether your answer is right if you don't have the differentiation function in your calculator? Thank you


That’s what practice is for.

I doubt you can have Wolfram in an exam which is why that’s important, but otherwise you can verify answers through it when grinding through problems.

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