X>1,则x-1>0X+4/(X-1)=(x-1)+4/(x-1)+1>=2根号【(x-1)*4/(x-1)】+1=2*2+1=5所以,当斗戚(x-1)=4/(x-1),即x=3时,取颤销肢得最小茄世值是:5