Factor 9z + using the gcf.

The given expression is 9z.

To factor out the greatest common factor (GCF), we need to find the largest number or variable that can divide evenly into all the terms of the expression. In this case, the GCF of 9z is simply 9.

Factoring out 9 from 9z, we get:
9z = 9 * z

So, the expression 9z can be factored as 9 * z.