Implicit differentiation help

Limits, differentiation, related rates, integration, trig integrals, etc.
kristinamarie
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Joined: Thu Jul 05, 2012 5:24 pm
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Implicit differentiation help

Postby kristinamarie » Thu Jul 05, 2012 5:41 pm

I have 2 questions on this assignment that I cant get done.
question 1 : 2x^3 + 3xy^2 - y^3 =0

Question 2: find the equation of the tangent to the curve xy^2 + 3x -3y=6. at the point (2,1)

After differentiation then do i set the function dy/dx to equal 0? and substitute for zero...find 2nd deriv then sub for 2 and 1?

FWT
Posts: 121
Joined: Sat Feb 28, 2009 8:53 pm

Re: Implicit differentiation help

Postby FWT » Fri Jul 06, 2012 12:23 am

kristinamarie wrote:question 1 : 2x^3 + 3xy^2 - y^3 =0

What are you supposed to do with this one?

kristinamarie wrote:Question 2: find the equation of the tangent to the curve xy^2 + 3x -3y=6. at the point (2,1)

After differentiation then do i set the function dy/dx to equal 0? and substitute for zero...find 2nd deriv then sub for 2 and 1?

For the second one, yeh, do the differentiation and solve for dy/dx. You have to get the deriv at (2,1), so plug the x and y in to get the number for dy/dx. This is y our slope for the tangent. Then do the point-slope thing to get your tangent line at the point.


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