Calculus Help: Find the limits - lim(x→-∞)⁡ xe^(-x) , lim(x→∞)⁡ xe^(-x) - Techniques

Here is the technique to solve this question: Calculus Help: Find the limits - lim(x→-∞)⁡ xe^(-x) , lim(x→∞)⁡ xe^(-x) - Techniques