x_1, x_2, x_3, x_4, x_5, 
-x_1*(x_4-1)
x_1*x_3-1
-2*x_2*x_5+x_1
x_1^2+x_2^2-1
-2*x_1*x_5-x_3*x_4+x_2+x_3
