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# C4 implicit differentiation watch

1. (x-y)^4 = x+y+5

so far i have done :

4 (x-y)^3 (1-dy/dx) = 1 + dy/dx

and the answer is : 4(x-y)^3-1 / 1+4(x-y)^3

How do i get to this answer step by step .
2. (Original post by charly2012)
(x-y)^4 = x+y+5

so far i have done :

4 (x-y)^3 (1-dy/dx) = 1 + dy/dx

and the answer is : 4(x-y)^3-1 / 1+4(x-y)^3

How do i get to this answer step by step .
Expand the left hand side - multiply all of 4(x-y)^3 by each term in the next bracket then proceed as normal.
3. didnt quite get to that weird answer
4. (Original post by charly2012)
(x-y)^4 = x+y+5

so far i have done :

4 (x-y)^3 (1-dy/dx) = 1 + dy/dx

and the answer is : 4(x-y)^3-1 / 1+4(x-y)^3

How do i get to this answer step by step .
There's no need to expand the (x-y)^3 brackets. You basically have:
A(1 - dy/dx) = 1 + dy/dx which can be rewritten as:
A - A(dy/dx) = 1 + dy/dx

I'm sure you can rearrange this to get the dy/dx terms on 1 side
5. sorry i am not quite sure what the middle steps are , i been working through it in many way but didnt really get the similar answer . an answer would be much appreciated !
6. (Original post by charly2012)
sorry i am not quite sure what the middle steps are , i been working through it in many way but didnt really get the similar answer . an answer would be much appreciated !
7. my working is :

4 (x-y)^3 (1-dy/dx) = 1 + dy/dx

and i am not sure from here !
8. any clue or answer by any chance
9. (Original post by charly2012)
any clue or answer by any chance
Post 4 told you how to do this

If you do not understand from that I think it would be best to ask your teacher
10. I didnt give up and tried to solve the problem : )

Is it correct , and is this ho you approach it after the 1st step

thanks .
11. ??
12. (Original post by charly2012)
??
Yes that's right!

You did the hard part which was the implicit differentiation - the rest was just rearranging an equation to get dy/dx on its own
13. Yea thank you for your hint , but to be honest i did not know you can multiply 4 (x-y)^3 BY (1-dy/dx)

Is it always like that .
14. (Original post by charly2012)
Yea thank you for your hint , but to be honest i did not know you can multiply 4 (x-y)^3 BY (1-dy/dx)

Is it always like that .
I think you need to take a step back and think about what you're asking

dy/dx is just some function. (1-(dy/dx)) is just another function. You can multiply this by another function...why would you NOT be able to do this??

15. (Original post by davros)
Yes that's right!

You did the hard part which was the implicit differentiation - the rest was just rearranging an equation to get dy/dx on its own
That is what I meant in the first reply albeit poorly worded. Oops.
16. (Original post by davros)
I think you need to take a step back and think about what you're asking

dy/dx is just some function. (1-(dy/dx)) is just another function. You can multiply this by another function...why would you NOT be able to do this??

I am able to , but what i normally do is differentiate it and put dy/dx on one side and take it out and then do the division. but i was bit too slow in proccessing that question . thanks for the tips

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