Question

What is the expression of x to the 2 -16 equivalent to

Answer 1

The simplest answer, in terms of powers of 2, is 

                                             1
                                      ---------------
                                             16
                                           2
                             4                                     16
Please note that 2     equals 16, and that 2       thus equals 16^4.

Thus, another form in which the answer can be expressed is 

          1                  1
------------- , or ----------- .    If you want to take this further, calculate
        4                      2
   16                  256



           1
--------------------
   (256)(256)

Answer 2

If you mean (x^2 -16), then x^2-16 = (x+4)*(x-4). This follows from the formula a^2 - -b^2=(a+b)*(a-b)