For this case we have that by definition, the GFC (greatest common factor) of two numbers is given by the greater number that is a factor of both numbers. Then, let:
[tex]15x ^ 2y ^ 3\\-18x ^ 3yz[/tex]
We decompose into factors:
15: 1,3,5,15
18: 1,2,3,6,9,18
The GFC is 3.
So, we have that the GFC of the expressions is:
[tex]3x ^ 2y[/tex]
Answer:
[tex]3x ^ 2y[/tex]