The results of limits of a some simple sequences is obvious if put a few first natural numbers to formulas like in these examples. lim_{n → ∞} 3n^2 = ∞, lim_{n → ∞} 5n^3 = ∞, lim_{n → ∞} 8n^5 = ∞, lim_{n → ∞} n^7 = ∞, lim_{n → ∞} (-3n^2) = -∞, lim_{n → ∞} (-5n^3) = -∞, lim_{n → ∞} (-8n^5) = -∞, lim_{n → ∞} 3/n^2 = 0, lim_{n → ∞} (-2/n) = 0, lim_{n → ∞} (-9/n^3) = 0.