x1+x2=-2,x1*x2=-1/3
所以x1^2+x2^2=(x1+x2)^2-2*x1*x2=14/3, x1^2*x2^2=(x1*x2)^2=1/9
以x1^2和x2^2为根的新方程为x^2-(x1^2+x2^2)*x+x1^2*x2^2=0
即x^2-14/3x+1/9=0化简得
9x^2-42x+1=0