f(x-2)=x^2-3x+1
用t代替x-2
则x=2+t
即f(t)=(2+t)^2-3(2+t)+1
=4+t^2+4t-6-3t+1
=t^2+t-1
用x代替上式的t
即f(x)=x^2+x-1