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    x^3(2x + 6)^4

    i have gotton down to:

    8x^2(8x^3 + 3x^2(2x + 6))

    I can't seem to simplyfy this one or have i gone wrong?

    Please help!
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    Make sure you're using the chain rule on (2x + 6)^4 to get V`, and then use the product rule
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    you haven't done product rule correctly.
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    (Original post by DeanK2)
    you haven't done product rule correctly.
    ok, i did it again and i got:

     8x^3(2x + 6)^3 + 3x^2 (2x + 6)^4

    is this one right cos i can't seem to simpifly it either! :confused:
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    (Original post by DreamsComeTrue.)
    ok, i did it again and i got:

     8x^3(2x + 6)^3 + 3x^2 (2x + 6)^4

    is this one right cos i can't seem to simpifly it either! :confused:
    Looks fine to me.
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    (Original post by Rocious)
    Looks fine to me.
    do you how to simplyfy this one?

    it says in the book to take  2x^2(2x + 6)^3 out of the brackets but i can't see how that works witht he second bit of the equation as i don't know how to take these complicated factors out!
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    No it's all wrong- i think!
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    You square the differential
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    Just start by taking x^2 out, and (2x+6)^3 out and see how it goes.
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    (Original post by PeeWeeDan)
    Just start by taking x^2 out, and (2x+6)^3 out and see how it goes.
    if i take  x^2 out, then what happens to the  3x^2 as thats not a product of x^2
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    (Original post by DreamsComeTrue.)
    if i take  x^2 out, then what happens to the  3x^2 as thats not a product of x^2
    3 times x^2 = 3x^2?
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    Square The Differential
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    (Original post by Rocious)
    3 times x^2 = 3x^2?
    oh yeah.. thats stupid of me!

    Taking x^2(2x + 6)^3 out gives..
     x^2(2x + 6)^3 (4x + 3(2x + 6))

    =  x^2(2x + 6)^3(10x + 18)

    then taking the 2 out gives:  2x^2(2x + 6)^3(5x+9)

    does that work?
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    (Original post by DreamsComeTrue.)
    oh yeah.. thats stupid of me!

    Taking x^2(2x + 6)^3 out gives..
     x^2(2x + 6)^3 (4x + 3(2x + 6))
    Why only 4x?

    Bearing in mind it's early, I could well be wrong.
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    (Original post by nicangeli)
    Why only 4x?

    Bearing in mind it's early, I could well be wrong.
    oh yeah, my mistake:

     x^2(2x + 6)^3 (8x + 3(2x + 6))

    =  x^2(2x + 6)^3 (14x + 18))
    taking out  2x^2(2x + 6)^3 (7x+9)

    yes! i think i've got it! thanks a lot!
 
 
 

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