Question 327832
4b^7 - 500b^4

1. GCF is 4b^4

= 4b^4(b^3 - 125)

2. Now you apply the factoring difference of two cubes:
a^3-b^3= (a-b)(a^2+ab+b^2)

= 4b^4(b-5)(b^2+5b+25)