X+ X-1分之3=X+3/(X-1)=X-1+3/(X-1)+1>=2*根号下[(X-1)*3/(X-1)] +1 --{算术平均数不小于几何平均数}=1+2倍根号3所以: X+ X-1分之3的最小值:1+2倍根号3
