设两根分别为x1,x2;则s1=-b/a;s2=(x1+x2)*2-2x1x2=(b*2-2ac)/a*2;s3=(x1+x2)*3-3x1x2(x1+x2)=(3abc-b*3)/a*3
cs1=-bc/a;bs2=-2abc/a*2;as3=(3abc-b*3）/a*2
最后答案等于 0