解:设t=x+1 则x=t-1 可得:f(t)=(t-1)^2-(t-1)+3 =t^2-3t+5可得:f(x)=x^2-3x+5f(x-1)=(x-1)^2-3(x-1)+5 =x^2-5x+9
f(x+1)=x^2-x+3=(x+1)^2-2x-1-x+3=(x+1)^2-3x+2=(x+1)^2-3(x+1)+5所以f(x)=x^2-3x+5,所以f(x-1)=(x-1)^2-3(x-1)+5=x^2-5x+9