1) Using the different factoring techniques
2) Items 1, 3. Factoring the greatest common factor
2, 9. Difference of two squares
5,6,7,8. Reverse FOIL method (looked for two binomials and used FOIL method to come up with the original expression)
3) To check if they are the right factors, use distribution or FOIL method.
4) #10 because it is not factorable.