Final answer:
The factored form of the expression 9a²-12a is 3a(3a - 4), factored by extracting the greatest common factor of 3a.
Step-by-step explanation:
The given mathematical expression is 9a²-12a. To factor this expression, we look for the greatest common factor (GCF) that both terms have. We see that both terms have a common factor of 3a. Factoring this out, we get:
3a(3a - 4)
This is the factored form of the given quadratic expression. We found the greatest common factor and then divided each term by this factor to determine the terms in the parentheses.