Chapter 1.5, Problem 2E

Explain what it means to say that

$\underset{x\to 1^{-}}{\lim }f\left(x\right)=3$ and $\underset{x\to 1^{+}}{\lim }f\left(x\right)=7$

Is this situation is it possible than $\underset{x\to 1}{\lim }f\left(x\right)$ exists? Explain.