Some steps to rewrite the expression x3 - 16x + x2 - 16 as a product of three factors are shown below: step 1: x3 - 16x + x2 - 16 step 2: x3 + x2 - 16x - 16 step 3: x2(x + 1) - 16(x + 1) which of the following best shows the next two steps to rewrite the expression?
a. step 4: (x2 + 16)(x + 1); step 5: (x + 4)(x + 4)(x + 1)
b. step 4: (x2 - 16)(x + 1); step 5: (x + 4)(x + 4)(x + 1)
c. step 4: (x2 - 16)(x + 1); step 5: (x - 4)(x + 4)(x + 1)
d. step 4: (x2 + 16)(x + 1); step 5: (x - 4)(x + 4)(x + 1)