What is square root of 4

It seems that after learning quadratic equation, some students confused about square root. They thought $\sqrt 4$ can be -2 or 2.

No! $\sqrt 4$ is $2$

But (you may say),  $(-2)^2$ is also 4. Doesn't it mean -2 is also $\sqrt 4$

Nope! By convention squared root of a positive number is always a positive number.

But, if you are asked to find x that fit in this equation $x^2 = 4$ the answer $x = \pm \sqrt 4$.

See here, the value of x that fit to that equation is $x = -\sqrt 4$ or $x= +\sqrt 4$ and $\sqrt 4$ is 2.

Hence the solution for x is -2 or 2