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Math Help - Chain rule

  1. #1
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    Chain rule

    I have differentiated two expressions but the book has different answers. They are (x^9+8x)^3 and (x^3-1)^5.

    Could someone give me the answers to check? I was using the chain rule and Leibniz notation.
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  2. #2
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    What is the exact problem - are those two expressions part of different problems? It is not clear from your question. Just rewrite the problem you wish to have assistance with.
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  3. #3
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    They are two different questions. The first equation is y=(x^9+8x)^3.
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  4. #4
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    Then by the chain rule (as in your other problem), F(G(x)) is equal to F'(G(x))G'(x):

    F'(G(x)) = 3(x^{9}+8x)
    G'(x)=9x^{8}+8
    F'(G(x))G'(x)=3(x^{9}+8x)(9x^{8}+8) \Rightarrow 3(9x^{17}+16x^{9}+64x)

    The second problem follows in the exact same way.
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  5. #5
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    You have missed ^2 from (x^9+8x). I'm new to this but I've found my mistakes. Thanks.
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