quick math question please help?

Question

I need to consider the following mathematical proof is it right ot wrong
let a=b
a squared=ab
a squared + a squared-2ab=ab+a squared-2ab
2(a squared - ab)= a squared - ab
2=1

Answer 1

You divided by zero, right after this line:

2(a^2 - ab)= a^2 - ab

Since we are given that a=b, and know that therefore a^2 = ab, and thus that (a^2 - ab) = 0... the above is really saying:

2*0 = 1*0

... which is true.

However, you can't divide by zero to cancel that out into "2 = 1."

A friend of mine wrote a much better proof of "1 = 2" at this link:
http://www.ninjasoft.com/ozone/zobi-wan/one-equals-two.jpg

Answer 2

You did a fallacy by dividing by (a^2 -- ab) which is zero as per second line.
Can you divide by zero? Certainly NOT.
Otherwise :
0 = 0
=> 100 -- 100 = 121 -- 121
=> 10^2 -- 10^2 = 11^2 -- 11^2
=> (10 + 10)(10 -- 10) = (11 + 11)(11 -- 11)
=> (10 + 10)(0) = (11 + 11)(0)
=> (10 + 10) = (11 + 11) dividing by (0)
=> 20 = 22
=> 10 = 11, do you agree?

Answer 3

Whoa! Not so fast!
You can only take out (a squared-ab) from both sides of the equation (in the last line ) IF and ONLY IF "a squared-ab" is NOT equal to zero. In your above example, sadly, it is.

Answer 4

Its right. 2=1.

Answer 5

Dividing by zero will screw up any proof.