Zorich Mathematical Analysis Solutions Guide

Exercise 3.1: Prove that the function $f(x) = x^2$ is continuous on $\mathbbR$.

Solution: Let $\epsilon > 0$. We need to show that there exists $N$ such that $|1/n - 0| < \epsilon$ for all $n > N$. Choose $N = \lfloor 1/\epsilon \rfloor + 1$. Then for all $n > N$, we have $|1/n - 0| = 1/n < 1/N < \epsilon$, which proves the result. zorich mathematical analysis solutions

Exercise 1.1: Prove that the set of rational numbers is dense in the set of real numbers. Exercise 3

Solution: Let $x_0 \in \mathbbR$ and $\epsilon > 0$. We need to show that there exists $\delta > 0$ such that $|f(x) - f(x_0)| < \epsilon$ for all $x \in \mathbbR$ with $|x - x_0| < \delta$. Choose $\delta = \min1, \epsilon/(1 + $. Then for all $x \in \mathbbR$ with $|x - x_0| < \delta$, we have $|f(x) - f(x_0)| = |x^2 - x_0^2| = |x - x_0||x + x_0| < \delta(1 + |x_0|) < \epsilon$, which proves the result. Choose $N = \lfloor 1/\epsilon \rfloor + 1$