Find x^3 + 3x if x =

\(If\ x = {(4+\sqrt{15})}^{1/3} + {(4 -\sqrt{15})}^{1/3}\)

\(Find \ x^3 - 3x\)

\((\sqrt[3]{4+\sqrt{15}}+\sqrt[3]{4-\sqrt{15}})^3-3(\sqrt[3]{4+\sqrt{15}}+\sqrt[3]{4-\sqrt{15}})\color{blue}=8\)

Calculated by http://www.wolframalpha.com/input/?i=48%2F2(9%2B3)%3F
Even I do not.

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Here are some intermediate steps:

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