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hiramoby

  • 3 years ago

Given xy=-9 find dy/dt when x = -7 and dx/dt=-7

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  1. hiramoby
    • 3 years ago
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  2. hiramoby
    • 3 years ago
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    the answers are in the screen shot

  3. hiramoby
    • 3 years ago
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    are you still there?

  4. hiramoby
    • 3 years ago
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    >>>???

  5. Australopithecus
    • 3 years ago
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    dy/dt xy = -9 dy/dt xy = -9 xy' = -9 y' = 9/7

  6. Australopithecus
    • 3 years ago
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    dx/dt xy = - 9 yx' = - 9 y(-7) = - 9 y =-9/-7 y = 9/7

  7. Australopithecus
    • 3 years ago
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    I think this is right just using implicit differentiation

  8. Australopithecus
    • 3 years ago
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    and chain rule

  9. Australopithecus
    • 3 years ago
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    do you understand how I got my answer?

  10. hiramoby
    • 3 years ago
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    Thank you, help me with my other question please. Yes I did , i was stuck after implicit.. thought it could not be this easy

  11. Australopithecus
    • 3 years ago
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    ok send me a link to your next question

  12. zepdrix
    • 3 years ago
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    @Australopithecus I'm confused by what you did in your steps. When you took the derivative, did you remember to apply the product rule? :o

  13. hiramoby
    • 3 years ago
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    austra i sent you a mail

  14. Australopithecus
    • 3 years ago
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    I dont need to apply the product rule because we are taking the derivative in respect to t not in respect to y or x so they are treated as constants

  15. Algebraic!
    • 3 years ago
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    no lol.

  16. zepdrix
    • 3 years ago
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    No both are variables, unless you're taking a partial derivative, you need to apply the product rule.

  17. Algebraic!
    • 3 years ago
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    both are functions of time.

  18. zepdrix
    • 3 years ago
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    I did the steps using the product rule and I also came up with 9/7... so maybe just a little bit of luck XD lol

  19. Australopithecus
    • 3 years ago
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    oh I guess so :)

  20. Algebraic!
    • 3 years ago
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    d/dt( x*y=-9) = dx/dt*y + x*dy/dt =0 dy/dt = -dx/dt *y/x

  21. Australopithecus
    • 3 years ago
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    can you break down the steps clearer algebraic!

  22. Algebraic!
    • 3 years ago
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    it's just use of the product rule on x*y =-9 then solving algebraically for dy/dt

  23. zepdrix
    • 3 years ago
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    |dw:1351050464937:dw| Leibniz notation (with the differentials) can be a little tricky to understand. Maybe if you see it with the primes it'll make some sense :o

  24. Australopithecus
    • 3 years ago
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    yeah that makes a lot more sense seeing as I had to take the derivative on both sides of the equation and I kept getting 0 Thanks for the refresher

  25. Algebraic!
    • 3 years ago
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    you do take the derivative on both sides and you do 'get 0'

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