Final answer:
The Greatest Common Factor (GCF) of 4x² and 9x is x.
Step-by-step explanation:
The Greatest Common Factor (GCF) of 4x² and 9x can be found by determining the highest power of a variable that appears in both terms and multiplying it by the GCF of the coefficients. The variable in this case is 'x.' The GCF of the coefficients, 4 and 9, is 1. The highest power of 'x' that appears in both terms is x. Therefore, the GCF of 4x² and 9x is 1x, or simply x.