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Homework Help: Find the equation of the tangent line to the graph

  1. Apr 26, 2005 #1
    i just want to check my answers...coz i don't have an answer key to compare with....
    1) y^2-3xy+x^2=7
    y'=3y-2x/2y-3x

    2) x^2+y^2=2xy
    y'=1

    3) 2x^2+xy+3y^2=0
    y'=-4x-y/x+6y

    4) 5x^2-2xy+7y^2=0
    y'=y-5x/7y-x

    5) 7x^2+6xy+9y^2=0
    y'=-7x-3y/3x+9y

    6) Find the equation of the tangent line to the graph of x^2+2y^2=3 at (1,1)
    ans: x+2y-3=0

    7) Find the equation of the tangent line to the graph of x^2+3y^2=4 at (1,1)
    ans: x+3y-4=0

    are those correct?
    Thanks for your time
     
  2. jcsd
  3. Apr 26, 2005 #2
    I'd look over those if they were latexed.. :P
    Thats too messy, but just integrate them and see if you get the original function.
     
  4. Apr 26, 2005 #3

    James R

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    I checked number 6, and it is correct, so I assume no. 7 is probably correct too.

    I have no idea what the questions were for 1 to 5, so can't help you there.
     
  5. Apr 26, 2005 #4
    Theyre implicit differntiation problems. I'll do #2:

    2) x^2+y^2=2xy

    2x + 2yy' = 2y + 2xy'

    2x - 2y = 2xy' - 2yy'

    2x-2y = y'(2x-2y)

    y' = 1
     
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