What is the greatest common factor of 42a5b3, 35a3b4, and 42ab4?

To get the GCF of the the expression, we look for the greatest factor of the expression:

42a5b3, 35a3b4, and 42ab4?

thus

(42a5b3, 35a3b4, 42ab4)

factoring b^3 which is the GCF of (b^3, b^4, b^4) we get:

b^3 (42a^5,35a^3b, 42ab)

next we factor our a which is the GCF of (a^5, a^3, a)

ab^3 (42a^4,35a^2b, 42b^4)

next we factor out 7 which is the GCF of (42,35,42)

7ab^3 (6a^4,5a^2b, 6b^4)

hence the GCF is:

7ab^3