x4, x3, x2, x1, a4, a3, a2, a1, 
(x1^2*x3-x1*x2^2)*x4-x1*x2*x3^2+x2^3*x3
5*a1*x1+a2*x2-3*a3*x3-7*a4*x4
-4*a4*x2*x4-5*a4*x3^2+(-5*a2*x1-6*a3*x2)*x3+2*a2*x2^2
-2*a4*x1*x4+(2*a3*x1+5*a4*x2)*x3+a2*x1*x2
a2*x1^2+2*a3*x1*x2+a4*x1*x3+2*a4*x2^2
(5*a2*x1+10*a3*x2+7*a4*x3)*x4-2*a3*x3^2+4*a2*x2*x3+10*a1*x2*x1
