The expression $x + 1$ is a linear function, and there are no restrictions on the value of $x$. This means that $x$ can take any real number.

Thus, the domain of $x + 1$ is all real numbers, and in interval notation, the domain is:

$(-\infty, \infty)$

Would you like more details or have any questions?

Here are 5 related questions to explore:

1. What is the range of $x + 1$?
2. How do you find the domain of a rational function?
3. What is the domain of the function $\frac{1}{x+1}$?
4. How do you express inequalities in interval notation?
5. What are the restrictions on the domain of square root functions?

Tip: Always check for possible restrictions like division by zero or square roots of negative numbers when determining the domain of a function.