If f(x) is such that f''(x)=(x^2-1)^2(x^2+1), then its inflection point(s) occ…

If f(x)f(x) is such that f′′(x)=(x2−1)2(x2+1)f''(x)=(x^2-1)^2(x^2+1), then its inflection point(s) occur at
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