解只需:b^2-a*c=0,(1-b)/2=b,a+c-2*b=0或者b^2-a*c=0,(1-b)/2=a,b+c-2*a=0或者b^2-a*c=0,(1-b)/2=c,a+b-2*c=0;解得:c = 1/3,a = 1/3,b = 1/3