Can you use $k-1$ in mathematical induction induction hypothesis
Rather than proving for the $k+1$ term?
Can you use $k-1$ in mathematical induction induction hypothesis
Rather than proving for the $k+1$ term?
Yes.
Step 1 in the mathematical induction is to get a base case true. Step 2 is to prove that the claim holds for any $k \in \mathbb{Z}^+ $ with the hypothesis that the claim is true for $k-1$.
Note the "any" in step 2, that must answer your question.