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\(x^4-x^3+x^2-x>0?\)
\(x^2(x^2-x)+x^2-x>0?\)
\((x^2-x)(x^2+1)>0?\)
x^2+1 will always be positive, so the second condition is:
\((x^2-x)>0\)
\(x(x-1)>0\)
Which is true if x>1 or x<-1. So we are looking if x is either greater than 1, or less than -1.

1) x>1 gives us one of our conditions, so this is sufficient

2) This will only happen if x>1 or x<-1. If x is some fraction, then x^3<x, so x cannot be in the range of -1<x<1. Sufficient.

D.
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