Question

Show that x² is not O(x*log(x))

Answer 1

$f(x)=O(g(x))$ if there exists a positive real number M and a real number x₀ such that

$|f(x)|\le Cg(x)$ for all $x\ge x_0$

$|x^2|>xlogx$ for positive integers.

So. x² is not O(x*log(x)).