When factoring a polynomial, explain the role and placement of the gcf and how to verify factoring is correct.

You can verify by finding numbers or polynomials that divide out evenly from the original numbers or polynomials. I'm assuming that this is for simple polynomial factoring so correct me if I'm wrong. The GCF is more or less like dividing the GCF. If you don't know how to find the GCFExample: 
4x-24 
factors of 4 are 1 and 4 
factors of 24 are 1, 2, 3, 4, 6, 8, 12, 24 
S4 divided by 4 is 1 and 24 divided by 4 is 6 
4(x-6)since the highest factor of 4 is 4 and 24 also has a factor of 4 then 4 is the greatest common factor. 

1.17+3.99a. you combine the terms with a to create 3.99 and the 1.17 stays because it has no like terms or a variable