There’s a way to check that. Or any similar problem with a square root.
Take what you think is the answer, 1 and square it. If you get -1, then yes, it is. If not, it isn’t.
1(1) = 1
Not -1, so no it is not.
The solution is an imaginary number. Using both real numbers and imaginary numbers is called ‘complex’.
The square root of -1 is called i. So i squared is -1.