ax^2+by+c=0两根为m和n则有am^2+bm+c=0和an^2+bn+c=0联立可得am^2+bm-an^2-bn=0a(m+n)*(m-n)+b(m-n)=0m+n=-b/amn=[(m+n)^2-(m^2+n^2)]/2m^2+n^2=[-b(m+n)-2c]/amn={(-b/a)^2-[-b(-b/a)-2c]/a}/2=(b^2/a^2-b^2/a^2+2c...