For lim as x --> -∞, how come lxl becomes -x? 1. The problem statement, all variables and given/known data When you take the limit of a rational function as x approaches (-∞), I am dividing the numerator and denominator by the x value with highest exponent. Supposing the highest x value is √(x^2), so I divide the numerator and denominator by lxl. Then how come, in cases of x--> -∞, I am supposed to replace lxl with -x? Does this question make sense?