(根号4x^2 -4x+1) 减(根号2x-3)^2
=根号(2x-1)^2-(根号2x-3)^2
=|2x-1|-|2x-3|
因为根号定义,有2x-3>=0,则2x-1>0
|2x-1|-|2x-3|
=2x-1-(2x-3)
=2