/sci/ - Science & Math

I have a problem. How do you simplify "(2√x)^2" to a form "4x - 4√x"? In the original task there was also "- 1" so I kept it because I didn't know is it part of the solution or not.

2√x - 1 | ()^2 (This is the original sentence)
(2√x)^2 + (-1)^2 | This is my assumption. I don't know if it's right
4x - 4√x + 1 | I don't know where this result came from.

I tried with the square of a binomial but I got a different result:

2√x - 1 | ()^2
(2√x)^2 + (-1)^2 | the square of a binomial, (a-b)^2 = a^2 - 2ab + b2
2^2 - 2 * 2 * √x + (√x)^2 + 1
4 - 4√x + x + 1

Please help me!!!