设f(x)=e^(x-1)-x,则f `(x)=e^(x-1)-1,令f `(x)=e^(x-1)-1=0,得x=1,当x<1时,f `(x)<0,x>1时,f `(x)>0.
故x=1是f(x)的极小值点,也是最小值点,且f(1)=0,所以f(x)>=f(1)=0,即f(x)=e^(x-1)-x>=0.
所以e^(x-1)>=x .