Since the square root of 9 is 3, we can simplify this as -√9 = -3. That's a negative integer. It also counts as a rational number and a real number.

Example 2

If x^{2} = -4, is x a real or imaginary number?

Answer

It's imaginary. To get x by itself, we need to take the square root of both sides. But the square root of -4 is 2i, which is imaginary. Check it out: (2i)^{2} = (2^{2})(i^{2}) = 4i^{2} = 4(-1) = -4.