Answer
$f(t)=(t-1)^2$
Work Step by Step
We are given that $x=t-1$
Re-write as: $t=x+1$
When $a$ has a positive value then , shift the function to the right for $a$ units and when $a$ has a negative value then , shift the function to the left for $a$ units
Now, $f(t-1) =(t-2)^2$ and $f(x)=(x+1-2)^2 =(x-1)^2$
So, we have: $f(t)=(t-1)^2$