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¬å¼ï¼1.(a+b)=a^2+2ab+b^2 2.(a-b)=a^2-2ab+b^2
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¬å¼:(a+b)(a-b)=a^2-b^2 ååç¸ä¹æ³ï¼ï¼x+aï¼ï¼x+bï¼=a^2+(a+b)x+ab
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¬å¼ï¼ï¼a+bï¼^3=a^3+3ab(a+b)+b^3; (a-b)^3=a^3-3ab(a-b)-b^3
a^3+b^3=(a+b)(a^2-ab+b^2); a^3-b^3=(a-b)(a^2+ab+b^2)
å å¼å解ï¼n+n^2+n^3+â¦+n^m=[n^(m+1)-n]/(n-1);
4m^4+n^4=(2m^2+n^2)^2-(2mn)^2=(2m^2+2mn+n^2)(2m^2-2mn+n^2)
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