x4, x3, x2, x1, t, 
x1^2*x2-t*x1+t*x3-7*x1+2
-x1^2*x2-t*x2+10*t*x4+6*x1
x3^2*x4+t*x1-t*x3-7*x3+2
-x3^2*x4-t*x2-t*x4+6*x3+1
