First find all the factors of 15y^3 and then all the factors of -20y
15y^3 = 3 , 5 , y, y, y
-20y = 2 , 4, 5, 10, y
The GCF is 5 and y. We choose 5 because it is the greatest number and common in both sets. We also choose one y because it is common in both sets and one y is the greatest common y.
Answer = 5y
You can also do this by using the prime factorization method.
First of all the negative signs will be excluded when finding the GCF. The GCF is calculated by multiplying together the highest power of each of the common factors.
15^3 can be split into,
3*5*y*y*y.
-20y into,
2*4*5*10*y.
We will choose 5 as it is the greatest common number in both sets and choose y as it is also common in both sets.
