Which number have no rational square root?

Answer 1

For example, in the case of integers: the square root of a positive integer is either an integer (in the case of perfect squares, such as the square root of 1, 4, 9, 16, etc.), or an irrational number (such as the square root of 2, 3, 5, 6, etc.).

Similar in the case of the square root of a rational number (fraction): if you don't specifically choose fractions with perfect squares in the numerator and denominator (e.g., 4/9), you will end up with an irrational square root.