Question

how do you do this ​

Answer 1

You square it so for example the first one would be 1

Answer 2

Answer:

The best choice is to use a calculator (the button is $\sqrt$), but if that is not an option here are a few tips.

If a perfect square ends with a 1, then the last digit of its square root has to be either 1 or 9.

If a perfect square ends with a 4, then the last digit of its square root has to be either 2 or 8.

If a perfect square ends with a 5, then the last  digit of its square root is definitely 5.

If a perfect square ends with a 6, then the last digit of its square root has to be either 4 or 6.

If a perfect square ends with a 9, then the last digit of its square root has to be either 3 or 7.

I took a look and all of them seem to be perfect squares so hopefully this helps!