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    Hey, i was looking for an insight into where ive gone wrong on the folllowing question:

    Differentiate y=(x+2)e-x

    i did the product rule and got
    Y=uv

    u= x+2
    du/dx= 1

    v= e-x
    dv/dx= -e-x

    so dy/dx= e-x + -e-x(x+2)

    but the mark scheme says its
    -e-x(x+1)

    thanks for the read, any help is appreciated
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    (Original post by TheGreat1)
    Hey, i was looking for an insight into where ive gone wrong on the folllowing question:

    Differentiate y=(x+2)e-x

    i did the product rule and got
    Y=uv

    u= x+2
    du/dx= 1

    v= e-x
    dv/dx= -e-x

    so dy/dx= e-x + -e-x(x+2)

    but the mark scheme says its
    -e-x(x+1)

    thanks for the read, any help is appreciated
    Your answer is correct - you should simplify it down. Can you see a factor which you can take out?

    EDIT: Maybe not. -e^-x(x+2) - this bit isn't right.
    EDIT2: Gah shutup Blazy.
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    (Original post by TheGreat1)
    Hey, i was looking for an insight into where ive gone wrong on the folllowing question:

    Differentiate y=(x+2)e-x

    i did the product rule and got
    Y=uv

    u= x+2
    du/dx= 1

    v= e-x
    dv/dx= -e-x

    so dy/dx= e-x + -e-x(x+2)

    but the mark scheme says its
    -e-x(x+1)

    thanks for the read, any help is appreciated
    What happens when you take out the common factor of -e^{-x}
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    (Original post by TheGreat1)
    Hey, i was looking for an insight into where ive gone wrong on the folllowing question:
    You can check that your answer is correct or otherwise by using your calculator. Set x = 1.5 or something and see what happens.

    There is usually no need for YOUR answer to look exactly like the answer in the mark scheme.
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    (Original post by TenOfThem)
    What happens when you take out the common factor of -e^{-x}
    the you should get -e-x(-1+(x+2))?

    if thats correct then theres the answer
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    (Original post by TheGreat1)
    the you should get -e-x(-1+(x+2))?

    if thats correct then theres the answer
    and -1+x+2 =
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    (Original post by TenOfThem)
    and -1+x+2 =
    alrighty, thanks for yours (and everyone elses) help
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    (Original post by TheGreat1)
    alrighty, thanks for yours (and everyone elses) help
    NP

    As Steve said ... your answer would have been accepted unless there was a format specified in the question
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    Its because the next question asked for d2y/dX2 so doing it in this format would have made the next part easier.
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    (Original post by TheGreat1)
    Its because the next question asked for d2y/dX2 so doing it in this format would have made the next part easier.
    ahhhhh

    I usually factorise if I can anyway

    it helps if you need to find turning points and/or differentiate again

 
 
 
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