{ diff(x1, t) = (1*k14*k5/(1 + k7*x2^k9)*x1*(2*k6/(1 + k8*x2^k10) - 1) + 1*k14*k11/(1 + k12*x1^k13)*x2)/k14,
  diff(x2, t) = ((-1)*k14*k11/(1 + k12*x1^k13)*x2 + 1*k14*2*k5/(1 + k7*x2^k9)*x1*(1 - k6/(1 + k8*x2^k10)) + (-1)*k14*k1*x2)/k14 }