Power Seriesmedium
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If f(x)=n=0xnf(x) = \sum_{n=0}^{\infty} x^n and g(x)=n=0(1)nxng(x) = \sum_{n=0}^{\infty} (-1)^n x^n, what is the coefficient of x2x^2 in the Cauchy product f(x)g(x)f(x) \cdot g(x)?