Some definitions:

a x + b x = x (a + b)You can verify that this is correct by multiplying out the factored expression on the right side and obtaining the original expression on the left side.
Factorable form or method used Example Common factor Difference of squares Quadratic trinomial, perfect square Quadratic trinomial, a = 1 Quadratic trinomial, a ≠ 1 Completing the square Grouping Sum or difference of cubes Polynomial