Do you have the 4th problem typed correctly? The two given numbers have no factor (other than 1) in common (i.e., they are relatively prime) so the GCF is 1.
48 = 2^4 * 3
Therefore, GCF of 16a^4 b^4 + 32a^3 b^5 - 48a^2 b^6 is 16a^2 b^4, so
16a^4 b^4 + 32a^3 b^5 - 48a^2 b^6 = (16a^2 b^4)(a^2 + 2ab - 3b^2) = (16a
