TITLE: Is limit of function -1/0 ok?
QUESTION [5 upvotes]: A quick question, i'm determining the limit of this function:
$$\lim_{x→1}\frac{x^2 - 2x}{x^2 -2x +1}$$
When I divide numerator and denominator by $x^2$ and fill in $1$, I get $-1/0$. This is an illegal form right? Or does it indicate it is going to $∞$ or $-∞$?

REPLY [2 votes]: $$\lim\limits_{x\to 1}\frac{x^2-2x}{x^2-2x+1}$$

$$=\lim\limits_{x\to 1}(x^2-2x)\lim\limits_{x\to 1}\frac{1}{x^2-2x+1}$$
$$=-1\cdot\lim\limits_{x\to 1}\frac{1}{\underbrace{x^2-2x+1}_{\to 0+}}=\color{red}{-\infty}$$