(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Prove that

|x+y|^{2}+ |x-y|^{2}= 2|x|^{2}+ 2|y|^{2}

ifxandyare elements of ℝ^{k}

2. Relevant equations

Ordinary stuff

3. The attempt at a solution

Got the first part, but I don't understand the parallelogram thing yet. The little sketch I drew didn't help.

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# Interpret this geometrically, as a statement about parallelograms.

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