Let a = b.

Hence, a^2 = ab.

So, 2a^2-2ab = a^2 - ab

2(a^2-ab) = 1(a^2-ab)

Hence, 2=1?!

I showed this to two maths teachers at my school who couldn't figure this... Let's see how you guys fare.

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- February 13th 2010, 12:44 PMSuperCalculusOdd proof - Can you spot the error?
Let a = b.

Hence, a^2 = ab.

So, 2a^2-2ab = a^2 - ab

2(a^2-ab) = 1(a^2-ab)

Hence, 2=1?!

I showed this to two maths teachers at my school who couldn't figure this... Let's see how you guys fare. - February 13th 2010, 12:47 PMicemanfan
The reason is because .

- February 13th 2010, 12:48 PMSuperCalculus
- February 13th 2010, 12:49 PMicemanfan
- February 13th 2010, 12:50 PMpickslides
- February 13th 2010, 12:54 PMpickslides
- February 13th 2010, 01:07 PMArchie Meade
- February 13th 2010, 01:10 PMSuperCalculus
- February 21st 2010, 01:17 PMAryth
- February 21st 2010, 04:33 PMintegral
It is not surprising. I have come to learn over the years, high school teachers are mostly idiots who only know what the school expects them to teach. Which is not much (Rofl)

- February 27th 2010, 01:16 AMBacterius
This one can be found on Wikipedia if my memory is correct. It is indeed a division by zero.

Quote:

high school teachers are mostly idiots who only know what the school expects them to teach.

- March 1st 2010, 10:22 PMharish21
- March 1st 2010, 10:37 PMDrexel28
- March 1st 2010, 10:55 PMBacterius
Aww, teaching is so much more, so much more effective when the teacher enjoys what he's talking about, it really gives a different feel to the lesson (as I experienced it in biology). Sadly this world is not about a better education but about higher profit :( (high school teachers are cheap to manufacture)

- March 8th 2010, 04:57 PMVertazontal
Ignoring the last equation and simplifying the second to last one, I got 2A^2-2A^2=A^2-A^2, which is of course 0=0.

I know it's late, but I didn't look at all your guys' answers and solved it on my own, and wanted to check if my solution was correct.