2=1?Math brain teasers require computations to solve.
Read this following proof carefully.
X^2=XY Multiply both sides by X
X^2-Y^2=XY-Y^2 Subtract Y^2 from both sides
(X+Y)(X-Y)=Y(X-Y) Factor both sides
(X+Y)=Y Cancel out common factors
Y+Y = Y Substitute in from line (1)
2Y = Y Collect the Y's
2 = 1 Divide both sides by Y
Now obviously, 2 doesn't equal 1. So what's wrong with this proof?
HintIt's in lines 4 and 5.
Answer'Cancelling' the common factors from line (4) to (5) means dividing by the factor (X-Y). Since X=Y, this is a division by 0, the results of which are undefined.
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