Question

what is the mistake in the following
a=b
a^2=ab
a^2-b^2=ab-b^2
(a+b)(a-b)=b(a-b)
a+b=b
b+b=b
2b=b
2=1

Answer 1

I want to say
a+b=b
To get here, each side is divided by (a-b),
which is dividing by zero

Answer 2

Dockworker each side is divided by (a-b)

Answer 3

Yes, which is why it's wrong. Dividing both sides by a-b is dividing by 0 if a=b.