x+1=t
x=t-1
f(t)=(t-1)^2-2(t-1)+3
=t^2-2t+1-2t+5
=t^2-4t+6
f(x-1)=(x-1)^2-4(x-1)+6
=x^2-2x+1-4x+10
=x^2-8x+11