k2*x2 - x1*(k1 + k7) + k5*x3 + k12*x7 + k17*x8 - x1*x5*(k13 + k18) - k6*x1*x4 
k1*x1 + k4*x3 + k16*x8 - x2*(k2 + k3 + k15) 
k3*x2 - x3*(k4 + k5) + k6*x1*x4 
k5*x3 + k9*x6 - k19*x4 - k6*x1*x4 - k8*x4*x5 
k9*x6 + k12*x7 - k14*x5 + k17*x8 - x1*x5*(k13 + k18) - k8*x4*x5 
k11*x7 - x6*(k9 + k10) + k8*x4*x5 
k10*x6 - x7*(k11 + k12) + k13*x1*x5 
k15*x2 - x8*(k16 + k17) + k18*x1*x5 
