Question

Please help me find a flaw in this presumedly bogus proof!

Theorem: 2 = 1.
Proof: Given a = b
a2 = ab
a2 – b2 = ab – b2
(a + b)(a – b) = b( a – b)
a + b = b
But a = b , so
a + a = a
2a = a
2 = 1

Answer 1

isn't (a-b)= 0. Isn't it a bad idea to divide by zero?

Answer 2

2 = 1, the first line is wrong

Answer 3

you can't divide by zero

Answer 4

Good work folks!