f(x+2)=3x^2+2x-1
设x+2=t
x=t-2
f(t)=3(t-2)^2+2(t-2)-1
=3(t^2-4t+4)+2t-4-1
=3t^2-12t+12+2t-5
=3t^2-10t+7
f(x)=3x^2-10x+7
f(x-1)=3(x-1)^2-10(x-1)+7