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Math Help - power series problem.

  1. #1
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    power series problem.

    looks like this: f(x) = x/(9+x^2)

    need to find the interval of convergence.

    thanks for any help.
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  2. #2
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    Quote Originally Posted by rcmango View Post
    looks like this: f(x) = x/(9+x^2)

    need to find the interval of convergence.

    thanks for any help.

    f(x) = x/(9+x^2) = x/9 [1+(x/3)^2]

    and the usual series expansion of 1/(1+(x/3)^2) is derived from that of
    1/(1+z), with z=(x/3)^2, which is convergent for |z|<1, so is convergent for
    |x|<3.

    RonL
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