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candiwonderland

  • 3 years ago

i need to find dy/dt when x=8 and dx/dt=10 for xy=4

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  1. anonymous
    • 3 years ago
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    \[xy=4\] and i guess \(x=x(t)\) and \(y=y(t)\) i.e. they are both functions of \(t\) so via the product rule you get \[x'(t)y+y'(t)x=0\]

  2. anonymous
    • 3 years ago
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    it is easy to write \(x'\) than \(\frac{dx}{dt}\)

  3. anonymous
    • 3 years ago
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    now if \(x=8\) then since \(xy=4\) you know \(y=\frac{1}{2}\)

  4. anonymous
    • 3 years ago
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    and you are told \(x'=10\)

  5. anonymous
    • 3 years ago
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    solve \[x'(t)y+y'(t)x=0\] which is now \[10\times \frac{1}{2}+y'\times 8=0\] for \(y'\)

  6. candiwonderland
    • 3 years ago
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    oh okay

  7. candiwonderland
    • 3 years ago
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    thanks!

  8. anonymous
    • 3 years ago
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    yw

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