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  1. #1
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    Expand this

    ((r-1)^2)(r+1)

    How do I expand this? Thanks,

    JN
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  2. #2
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    Quote Originally Posted by Jim Newt View Post
    ((r-1)^2)(r+1)

    How do I expand this? Thanks,

    JN
    Rewrite the term:

    (r-1)^2 \cdot (r+1)= (r-1)(r-1)(r+1) = (r-1)(r^2-1) = r^3-r^2-r+1
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  3. #3
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    Hello,

    Quote Originally Posted by Jim Newt View Post
    ((r-1)^2)(r+1)

    How do I expand this? Thanks,

    JN
    You can do this in two ways :

    - develop (r-1)^2 by using the identity : (a-b)=a-2ab+b, then multiply by (r+1). But this will make a multiplication 3 terms by 2 terms

    - write : (r-1)^2=(r-1)(r-1) \implies ((r-1)^2)(r+1)=(r-1){\color{red}(r-1)(r+1)}

    Use the identity : (a-b)(a+b)=a-b
    Then, it will be a multiplication 2 terms by 2 terms, which is more beautiful
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