Maurizio T. answered 08/09/13
Statistics PhD and CFA charterholder with a true passion for teaching.
Maira, if I am reading this right, you are given the following binomial:
16x4 - 1
and you are asked to factor it.
Well, you should recall that, in general, if you are given something like
a4-b4
you can factor it as follows
a4-b4 = (a2+b2)(a2-b2).
Now the first term, (a2+b2), cannot be factored anymore, but the second one can be further factored as
(a2-b2) = (a+b)(a-b). Hence, we find:
a4-b4 = (a2+b2)(a2-b2) = (a2+b2)(a+b)(a-b).
Back to your case: let 16x4 = (2x)4 be your a4 and 1 = 14 be your b4 and use the result we just got for a4-b4.......................
[You will establish that the only possible correct answer among the alternatives given is (c)]