To factor the expression \(81x - 36\), we first notice that both terms have a common factor.
The greatest common factor (GCF) of \(81\) and \(36\) is \(9\).
So we can factor out \(9\):
\[ 81x - 36 = 9(9x - 4) \]
Thus, the correct factorization of the expression \(81x - 36\) is:
9(9x - 4)
This corresponds with the option:
9(9x−4).