Factor out the GCF

[SavannahAshley]

a^7b^8-a^4b^3+a^3b^6-a^3b^3
I started off with grouping the first two and the second two together
(a^7b^8-a^4b^3)+(a^3b^6-a^3b^3)
then I began to factor out the GCF
a^4b^3(a^3b^5-1)+a^3b^3(b^3-1)
on mymathlab, it says my answer is equivalent to the correct one, but its wrong :?

 

[wjm11]

a^7b^8-a^4b^3+a^3b^6-a^3b^3
I started off with grouping the first two and the second two together
(a^7b^8-a^4b^3)+(a^3b^6-a^3b^3)
then I began to factor out the GCF
a^4b^3(a^3b^5-1)+a^3b^3(b^3-1)
on mymathlab, it says my answer is equivalent to the correct one, but its wrong

If the instructions are to factor out the GCF, do not create separate groups; you must look at all of the terms at once. Notice that all of your terms have “a” as a factor, the smallest being a^3. Notice, also, that all of your terms have “b” as a factor, with b^3 being the smallest. Therefore, your GCF is (a^3)(b^3).

a^7b^8-a^4b^3+a^3b^6-a^3b^3 = (a^3)(b^3)(a^4b^5 – a + b^3 – 1)