13.

In this case, there is a common factor that we can factor out.

The expression inside the parentheses is then one of the easier

factoring problems.

If we do not factor out the common factor first, the problem

can still be done. Multiply the first and last coefficients, and find a

pair that add up to the middle one.

The FOIL step, then, looks like

This will factor as

which looks a little different from out other answer. But if you notice,

both of the terms in the first binomial factor have a common factor

of 2 which can be factored out,

leaving us with the same factors we got when we did the problem

the other way.

If there is a common factor that can be factored out, one will

have a choice between whether to factor it out at the beginning or to

factor it out later. You will find that it will make your job easier if

you factor out the common factor at the beginning of the problem.