当x≥2,则x-2≥0 x-1≥0,则f(x-2)=2 f(x-1)=2,g(x)=(6-2)/2=2当1≤x<2,则x-2<0, x-1≥0 则f(x-2)=1, f(x-1)=2 则g(x)=(6-1)/2=2.5当x<1 则 x-2<0, x-1<0 则f(x-2)=1, f(x-1)=1 ,则g(x)=(3-1)/2=1所以g(x)=2 ,x≥2 g(x)=2.5 1≤x<2 g(x)=1, x<1