2008-08-07 練習 mimetex [tex:(x+a)(x+b)=x^2+ax+bx+ab=x^2+(a+b)x+ab] [tex:(x+a)(x+b)(x+c)=(x^2+ax+bx+ab)(x+c)=x^3+ax^2+bx^2+abx+cx^2+acx+bcx+abc=x^3+(a+b+c)x^2+(ab+bc+ac)x+abc] …あってる?