k7*x4 - k6*x1 - k5*x1 + k4*x2*x3 
k5*x1 - k4*x2*x3 
k5*x1 - k4*x2*x3 
k6*x1 - k7*x4 
x1 - k8 + x2 + x4 
x1 - k9 + x3 + x4 
