Can a deductive argument be invalid

Can a deductive argument be invalid?

It has said that deductive argument are attempt to show that a conclusion necessarily follows from a set of premises or hypotheses.
A deductive argument is valid if the conclusion does follow necessarily from the premises.

If so, should all deductive argument are valid? According to the definitions above, they are the same thing, right? Then why there are deductive argument that are invalid?
Can you give me some examples? Thanks.

Other Answers:

Maybe ones that have no errors but lead to an extraneous solution, like:
If v(2 - x) = x
Then 2 - x = x^2 (square both sides)
0 = x^2 + x - 2 (rearrange terms)
0 = (x + 2)(x - 1) (factor)

0 = x + 2 (divide both sides by (x - 1) assuming x ? 1)
-2 = x (add -2 to both sides)

No errors yet x cannot be -2