9
9 (92 = 81)
If the square root is a whole number, then the square of the square root, the original number, is also a whole number; all whole numbers can be expressed as themselves over 1, and so are rational numbers. The answer is thus any square number, ie the square of the natural numbers: 1 (1²), 4 (2²), 9 (3²), 16 (4²), etc.
9 is the best estimate whole number
9 and 10
It is none of those because the square root of -9 is an imaginary number but the square root of 9 is 3 which is a rational integer or whole number
The square root of 79 is approximately 8.89. Rounding to the nearest whole number, the approximate square root of 79 is 9.
Yes. The square of a whole number is always a whole number. For example, 3 squared is 9, so the square root of 9 is 3. What you never have, is the square root of a whole number being a fraction that is not a whole number. The square root of a whole number is either a whole number or an irrational number. For example, the square root of 2 is irrational, because there are no 2 whole numbers a and b such that a/b squared is 2. This is not terribly difficult to prove, but I have already said too much; I have answered your question.
9
Yes. For example, the square root of 1/9.
For a number to be a perfect square, the number's square root has to be a whole number. 9 is a perfect square because its square root is a whole number, 3. If the square root of the number is a decimal, then it is not a perfect square. For example, 13 does not divide evenly so it not a perfect square.
Yes, it is +3 or -3
9
9 x 9 = 81 and 10 x 10 = 100. So any number 82-99 would have a square root between 9 and 10.
3 is the square root of 9. 9 is a square number. 9 is the square root of 81. 81 is a square number.
9 (92 = 81)
They are -9 and 9.