[ Diff(x[1], t) = (1*k[7]*k[1] + (-1)*k[7]*k[2]*x[1] + (-1)*k[7]*k[3]*x[1]*x[2])/k[7],
  Diff(x[2], t) = (1*k[7]*k[4]*k[3]*x[1]*x[2] + (-1)*k[7]*(k[2] + k[5])*x[2])/k[7] ]