Find the least integer n such that f(x) is O(xn) for each of these functions
a) f(x)=2x^2+x^3 logx
b) f(x)=3x^5+(logx)^4
c) f(x)=(x^4+x^2+1)/(x^4+1)
d) f(x)=(x^3+5logx)/(x^4+1)
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