a=(a1,a2),b=(b1,b2),c=(c1,c2)
a1x^2 b1x c1=0;a2x^2 b2x c2=0,a1b2-a2b1≠0;
可解得:x^2=(b1c2-b2c1)/(a1b2-a2b1);x=(c1a2-c2a1)/(a1b2-a2b1)
若(b1c2-b2c1)/(a1b2-a2b1)
a=(a1,a2),b=(b1,b2),c=(c1,c2)
a1x^2 b1x c1=0;a2x^2 b2x c2=0,a1b2-a2b1≠0;
可解得:x^2=(b1c2-b2c1)/(a1b2-a2b1);x=(c1a2-c2a1)/(a1b2-a2b1)
若(b1c2-b2c1)/(a1b2-a2b1)