help with this problem?

Question

Some students simplify
2x^2 - 32
------------
x - 4
as
2x - 8
--------
bottom cancels out..

Choose the values of x to show this is not true. then simplify it correctly?
how do i do this? im completely lost..

Answer 1

2(x^2 - 16) / (x-4) = 2(x+4)(x-4) / (x-4) = 2(x+4) or 2x + 8
for all values of x

except when x = 4

Answer 2

Choose x = 0:
The expression equals -32/ -4 = 8
The 2x - 8 equals -8

Factor the top first 2x^2 - 32 = 2(x^2 - 16) = 2(x + 4)(x - 4)
The expression becomes:
2(x + 4)