How to simplify 4 - 2 root 3 by 2

4 - 2root3 2

= 2 (2 - root3 ) / 2

= 2 -  root3  as the root 2 which we take as common is divided by 2 and the it will become 1 and when we multiply 

1 with the numbers in the bracket the numbers will remain same and that will be the final answer