📘 algebra, linear algebra, calculus

1. **Problem 1: Find the limit** $$\lim_{x \to 1} \frac{x^2 - 1}{x^2 + 1}$$ 2. Substitute $x=1$: numerator is $1^2 - 1 = 0$, denominator is $1^2 + 1 = 2$, so limit is $0/2=0$ direc