Question
What is wrong with the following "proof'? Let $x=y .$ Then $$\begin{aligned}x^{2} &=x y \\x^{2}-y^{2} &=x y-y^{2} \\(x+y)(x-y) &=y(x-y) \\x+y &=y \\2 y &=y \\2 &=1 \end{aligned}$$.
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Step 1: We start with the given equation $x=y$. Show more…
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