Alternative proof:
Suppose, P = NP
P² = P(NP)
(subtracting (NP)²)
P² - (NP)² = P(NP) - (NP)²
(dividing both sides by P-(NP)):
P + (NP) =(NP)
since P = NP (initial assumption):
2*P = P
(dividing by P):
2 = 1
which is a contradiction, therefore P \not= NP