Answers

①(a-b)^2=a^2+b^2-2ab
=(a+b)^2-2ab-2ab
=(a+b)^2-4ab

①の答えを使う
両辺√つけると出ます
③a^2-b^2=(a+b)(a-b)
②の答えを使います

ありがとうございます!

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