Answer :
It is good equation. Look, that:
81 = 3 x 3 x 3 x 3 = 3^4.
So you have to solve:
3^x = 3^4
exponents have to be the same, so
x=4
That's mean that A(4) = 81
81 = 3 x 3 x 3 x 3 = 3^4.
So you have to solve:
3^x = 3^4
exponents have to be the same, so
x=4
That's mean that A(4) = 81