complex i

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stupid

Joined Oct 18, 2009
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±hi georacer,
its not homework but m doing self study on basic maths related to signals & systems.

the eq is \(^{x^3-15x-4=0}\)
then x=\(\sqrt[3]{2+\sqrt{-121}}\)+\(\sqrt[3]{2-\sqrt{-121}}\)

(2±i)\(^{3}\)=2±i11=2±\(\sqrt{-121}}\)

x=(2+i)+(2-i)=4

i m wondering what method to arrive at the last stage.

hope someone shed lite on that.
thanks
Is that a homework question? Care to post the whole of the question?
 
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