Suppose $(b_a)^2=71_a$, where $a$ and $b$ represent two distinct digits. If $b=a-1$, find $a$.

I think the question is about 2 numbers a, b in other bases. For example: 8^2 in base 9 =71 in base 9.

Since it says: b=a - 1, then since b=8 and a =9, then b=9 - 1=8, which agrees with above.