let X=1

X=1
X^2=1
X^2 -1 = 0
(X+1)(X-1) = 1 (difference of two squares)
(X+1) = 1 (divide both sides by (X+1))
put X=1 in and:
(1+1) = 1
2 = 1?????
Where is the error?

Thios one took me a while to figure out, then, when I saw the light, I kicked myself to hard I convinced myself never to kick myself again.