To factor the expression \(9z + 18\) using the greatest common factor (GCF), we first identify the GCF of the terms.
- The terms are \(9z\) and \(18\).
- The GCF of the coefficients \(9\) and \(18\) is \(9\).
- We can factor out \(9\) from each term:
\[ 9z + 18 = 9(z) + 9(2) \]
Now, we can factor out the \(9\):
\[ 9(z + 2) \]
Thus, the factored form of \(9z + 18\) is:
\[ 9(z + 2) \]