AsymptoticEqual
AsymptoticEqual[f, g, x -> x*] gives conditions for f(x) ≍ g(x) or f(x) ∈ Θ(g(x)) as x -> x*.
AsymptoticEqual[f, g, {x1, ..., xn} -> {x1*, ..., xn*}] gives conditions for the multivariate case.
Examples
Test asymptotic equality:
AsymptoticEqual[x^2 + x, x^2, x -> Infinity]
(* True *)Please visit the official Wolfram Language Reference for more details.