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** <math>(ax+b)(cx+d) = acx^2 + (ad+bc)x + bd</math>
* 累乗
** <math>(a+\pm b)^2 = a^2 +\pm 2ab + b^2</math>
** <math>(a-\pm b)^23 = a^23 -\pm 2ab3a^2b + b3ab^2 \pm b^3</math>
** <math>(a+\pm b)^34 = a^34 +\pm 3a4a^2b3b + 3ab6a^2b^2 \pm 4ab^3 + b^34</math>
** <math>(a-\pm b)^35 = a^35 -\pm 3a5a^2b4b + 3ab10a^3b^2 -\pm b10a^2b^3 + 5ab^4 \pm b^5</math>
** <math>(a+b)^4 = a^4 + 4a^3b + 6a^2b^2 + 4ab^3 + b^4</math>
** <math>(a-b)^4 = a^4 - 4a^3b + 6a^2b^2 - 4ab^3 + b^4</math>
** <math>(a+b)^5 = a^5 + 5a^4b + 10a^3b^2 + 10a^2b^3 + 5ab^4 + b^5</math>
** <math>(a-b)^5 = a^5 - 5a^4b + 10a^3b^2 - 10a^2b^3 + 5ab^4 - b^5</math>
** <math>(a+b)^n = \sum_{r = 0}^n{}_n{\rm C}_{r} a^{n-r} b^r</math>
* 応用
** <math>(a+b)(a-b) = a^2 - b^2</math>
** <math>(a+\pm b)(a^2 -\mp ab + b^2) = a^3 +\pm b^3</math>
** <math>(a-b)(a^2 + ab + b^2) = a^3 - b^3</math>
** <math>(a+b+c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca</math>
** <math>(a+b+c)^3 = a^3 + b^3 + c^3 + 3ab^2 + 3ac^2 + 3ba^2 + 3ca^2 + 6abc + 3bc^2 + 3cb^2</math>
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