Mistake in description of rational expressions in math textbook?

Question

Mathematics

In the book "The Big Handbook of Mathematics" ed. Scanavi in ​​the chapter on identical transformations has the following list of algebraic expressions:

It is said that the first and second are rational.
The third and fourth are not. With the latter, everything is clear (there is a variable under the radical sign). And why is number 3 not a rational algebraic expression?

Answer 1

https://ru.wikipedia.org/wiki/Rational_expression
The second and third expressions are rational, the first and fourth are not. There is a typo in the book.