y=1/2+根号x-1/2+根号1/2-x
x-1/2大于等于0,1/2-x大于等于0,所以x=1/2,y=1/2
|2y-1|+5x-根号y2-2y+1 =|2*（1/2）-1|+5*1/2-根号（y-1）的平方
=0+5/2+1/2
=3