
The 2=1 puzzle
Dr Yan tests out a mathematical equation that seems to prove that 2=1. Or does it? Try the equation at home and see if you can spot the 'trick'?
a=b
[multiply both sides by a]
a×a = a×b
[add a×a to both sides]
a×a + a×a = a×a + a×b
[subtract 2×a×b from both sides]
a×a + a×a - 2×a×b = a×a + a×b - 2×a×b
[You can re-write this as following:]
2×a×a - 2×a×b = a×a - a×b
[This can then be represented as:]
2(a×a - a×b) = 1(a×a - a×b)
[Divide both sides by (a×a - a×b)]
2=1
Duration:
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