what is the greatest common factor of 10x^6y^4 and 20x^7y^8

The greatest common factor of 10x^6y^4 and 20x^7y^8 is 10x^6y^4.

This is because the greatest common factor is the largest expression that can divide evenly into both terms. In this case, 10x^6y^4 is the largest expression that can divide evenly into both 10x^6y^4 and 20x^7y^8.