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takuto March 13th, 2010 09:01 PM

Derivatives Help
 
Hi. I have problems with derivatives. I was absent one day from class and I still have to do the homework. I'd greatly appreciate if anyone could help me with some problems. Thanks. The instructions:

Find dy/dx:
1) 5x^(4/5)+10y^(6/5)=15
2) sqrt(xy)=1
3) y^2= (x) / (x+1)


Any help would be greatly appreciated.

skipjack March 13th, 2010 10:54 PM

You should revise the differentiation rules.

2) sqrt(xy) = 1 implies y = 1/x, so dy/dx = -1/x.
3) y = 1 - 1/(x + 1), so 2ydy/dx = 1/(x + 1), and so dy/dx = 1/(2y(x + 1)).

What progress can you now make with the first equation?


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