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# P3 Implicit Differentiation Question watch

1. Hey, Im stuck on this question - just getting to understand implicit diff but this one I get stuck on one part.

-Differentiate 2x^2 + 3xy -4y + y^2 =5

I know you have to implicitly different 3xy [ which is what I cant do] and Y^2 [ I can do this]

So right now I am at this stage of this question ...--

4x^2 + d/dx (3xy) - 4dy/dx + 2y dy/dx = 0

Can anybody just explain to me how I would implicitly differentiate the 3xy

2. Use product rule for d/dx[3xy]:

= 3[(1)(y) + (x)(dy/dx)] ...

When you differentiate the 'x' with respect to x, you get 1, and then mulitply by y.
When you differentiate 'y' with respect to x, you get dy/dx, and then muitply by x.

http://www.thestudentroom.co.uk/show....php?p=2162948
4. implicitly differntiating 3xy means u have to use the product rule methinkz

differnt 3xy = (3)(y) + (3x)(dy/dx) = 3y + 3x(dy/dx)

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