[고교 수학] 곱셈 공식

(1-1) (𝑥＋𝑦)² = 𝑥²＋2𝑥𝑦＋𝑦²

(1-2) (𝑥－𝑦)² = 𝑥²－2𝑥𝑦＋𝑦²

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(2) (𝑥＋𝑦)(𝑥－𝑦) = 𝑥²－𝑦²

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(3) (𝑥＋𝑎)(𝑥＋𝑏) = 𝑥²＋(𝑎＋𝑏)𝑥＋𝑎𝑏

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(4) (𝑎𝑥＋𝑏)(𝑐𝑥＋𝑑) = 𝑎𝑐𝑥²＋(𝑎𝑑＋𝑏𝑐)𝑥＋𝑏𝑑

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(5) (𝑥＋𝑦＋𝑧) = 𝑥²＋𝑦²＋𝑧²＋2𝑥𝑦＋2𝑦𝑧＋2𝑧𝑥

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(6-1) (𝑥＋𝑦)³ = 𝑥³＋3𝑥²𝑦＋3𝑥𝑦²＋𝑦³

(6-2) (𝑥－𝑦)³ = 𝑥³－3𝑥²𝑦＋3𝑥𝑦²－𝑦³

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(7-1) (𝑥＋𝑦)(𝑥²－𝑥𝑦＋𝑦²) = 𝑥³＋𝑦³

(7-2) (𝑥－𝑦)(𝑥²＋𝑥𝑦＋𝑦²) = 𝑥³－𝑦³

(2020.06.11.)