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# implicit differiantion, can't get the numerator correct :S watch

1. Okay im just practising some questions and the question is,

If find dy/dx in terms of x and y

okay for this part i did:

then this is the part im stuck on:

Show that

i tried using quotient rule however i put everything in terms of x to make it easier to differentiate but that becomes nasty and no where near the answer, i did this by re arranging the first eq to make x the subject:

x= (2y-y^2)^1/2

then subbed this into the x/ (1-y) then proceeded with the quotient rule and ended up getting:

1/(2y-y^2)^ 1/2 + (2y-y^2)^ 1/2 / (1-y)^2

i then tried using product rule by changing the first differential into x(1-y)^-1 and got closer...

i got:

So yeahhh... someone show me what im doing wrong...
2. Might look into where you made your error if I'm still awake in a little bit, but I would advise just differentiating x/(1-y) implicitly. You can then replace any dy/dx s with the formula you got for that. Seems simpler to me.
3. (Original post by Slumpy)
Might look into where you made your error if I'm still awake in a little bit, but I would advise just differentiating x/(1-y) implicitly. You can then replace any dy/dx s with the formula you got for that. Seems simpler to me.
hmm okay ill try this now
4. (Original post by a10)
hmm okay ill try this now
Your error is when you do the second differentiation. Have a look at your result, and think about why it might be wrong (the one where you use the quotient rule). Without your workings for the product rule, I don't know what you've done (although my suspicion is a similar mistake).
5. (Original post by Slumpy)
Your error is when you do the second differentiation. Have a look at your result, and think about why it might be wrong (the one where you use the quotient rule). Without your workings for the product rule, I don't know what you've done (although my suspicion is a similar mistake).
fudge i forgot to differentiate implicitly

okay thanks ill try thiis
6. (Original post by Slumpy)
.
thank you, i solved it now

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Updated: November 19, 2013
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