[ Eq(1*k21*x1 + 1*k21*x2 + 1*k21*x3 + 1*k21*x4, k21*k25),
  Eq(1*k21*x5 + 1*k21*x6 + 2*k21*x8 + 1*k21*x9 + 1*k22*x12 + 2*k22*x13 + 1*k22*x14 + 1*k22*x15, k21*k26 + k22*k27),
  Eq(1*k21*x7 + 1*k21*x9 + 1*k22*x15 + 1*k22*x16, k21*k28 + k22*k29) ]