What is the greatest common factor of 28x²y-7xy^5?

The greatest common factor of this can be solved by looking at the individual parts and splitting it up.

First, we have 28 and 7.  Well, thats an easy one.  7 goes into 28 4 times so we are now left with 4 and 1.

We can also write the rest of this like this 4(x*x*y) - 1(x*y*y*y*y*y)

Now, what values are in both equations.  We have one x and one y that can be taken out of both.

We end up with 7xy(4x-7y^4)

7xy would be the greatest common factor. You can divide both terms by 7xy. 7 goes into 28 4 times ad you can factor out both an x and a y from both terms. You would end up with: 7xy(4x-y^4).