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Math Help - Linearly independent real solutions

  1. #1
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    Linearly independent real solutions

    Find all numbers r, real and complex, such that e^rx is a solution. Find two linearly independent real solutions.

    (D^2 + 9)y = 0

    Here's how I tried to solve it:
    1. r^2 + 3^2 = 0
    2. r^2 = -3^2
    3. r = 3i

    So two independent linear solutions would be: cos 3y and sin 3y
    Does this look about right?

    Thanks,
    Jim
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  2. #2
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    Opalg's Avatar
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    Quote Originally Posted by Jim Newt View Post
    Does this look about right?
    Yes.
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