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anonymous

  • 5 years ago

1) find d^2f/dx^2 when f(x) = x e^-7y+5y 2) find d^2f/dx dy when f(x) = x e^-8y+3y

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  1. anonymous
    • 5 years ago
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    two different questions here question (1) find d^2f/dx^2when f(x) = x e^-7y+5y question (2) find d^2f/dx dy when f(x) = x e^-8y+3y

  2. amistre64
    • 5 years ago
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    deriveing twice I assume

  3. amistre64
    • 5 years ago
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    do we do partials? or implicits?

  4. amistre64
    • 5 years ago
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    well, since f(x) implies one variable id conjecture implicits

  5. dumbcow
    • 5 years ago
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    hmm since its wrt x and both are linear wrt x then the 2nd derivatives are 0

  6. amistre64
    • 5 years ago
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    \[ x e^{-7y} + 5y\] by chance?

  7. dumbcow
    • 5 years ago
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    oh i was assuming partial

  8. amistre64
    • 5 years ago
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    those groupings are a pain if you dont get them right

  9. amistre64
    • 5 years ago
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    x e^(-7y) + 5y x' e^(-7y)+ x e^(-7y)' + 5 y' e^(-7y) -7x e^(-7y) y' + 5 y' then again

  10. anonymous
    • 5 years ago
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    i have loads of these, need to be handed in ten minutes haha

  11. amistre64
    • 5 years ago
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    the second one there suggests partials but its only a single variable

  12. dumbcow
    • 5 years ago
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    amistre, you are finding dy/dx not df/dx though

  13. amistre64
    • 5 years ago
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    f(x) assumes that all variables are functions of x, so y = y(x)

  14. amistre64
    • 5 years ago
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    the 2nd on tho says f(x) and wants f_xy

  15. dumbcow
    • 5 years ago
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    i think it should be written f(x,y) otherwise it would have asked for dy^2/dx right?

  16. amistre64
    • 5 years ago
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    i think there might be some confusion as to whether f(x) IS y rather than written out is a rule with x(x) and y(x)

  17. amistre64
    • 5 years ago
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    hard for me to parse the intricate details tho :)

  18. dumbcow
    • 5 years ago
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    agreed...salman little help?

  19. anonymous
    • 5 years ago
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    its d^2f/dx dy the f(x)=xe^-8y+3y sorry chaps, this is the only info i have

  20. dumbcow
    • 5 years ago
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    ok, then assuming f(x) is not y, y is just another variable df/dx = e^-8y d/dy e^-8y = -8*e^-8y

  21. dumbcow
    • 5 years ago
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    for part a) df/dx = e^-7y d/dx e^-7y = 0

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