YES
O(n^4)
TRS:
 {
              __(X, nil()) -> X,
           __(__(X, Y), Z) -> __(X, __(Y, Z)),
              __(nil(), X) -> X,
                 U12(tt()) -> tt(),
                 U11(tt()) -> U12(tt()),
  isNePal(__(I, __(P, I))) -> U11(tt()),
               activate(X) -> X
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
                __(X, nil()) -> X,
             __(__(X, Y), Z) -> __(X, __(Y, Z)),
                __(nil(), X) -> X,
                   U12(tt()) -> tt(),
                   U11(tt()) -> U12(tt()),
    isNePal(__(I, __(P, I))) -> U11(tt()),
                 activate(X) -> X
   }
  Matrix Interpretation:
   Interpretation class: triangular
              [X3]    [1 0 0 0][X3]   [1]
              [X2]    [0 1 0 0][X2]   [0]
   [activate]([X1]) = [0 0 1 0][X1] + [0]
              [X0]    [0 0 0 1][X0]   [0]
   
             [X3]    [1 0 1 0][X3]   [0]
             [X2]    [0 0 1 0][X2]   [0]
   [isNePal]([X1]) = [0 0 0 0][X1] + [1]
             [X0]    [0 0 0 0][X0]   [1]
   
         [X3]    [1 0 1 1][X3]   [1]
         [X2]    [0 0 1 0][X2]   [0]
   [U11]([X1]) = [0 0 0 0][X1] + [1]
         [X0]    [0 0 0 0][X0]   [1]
   
          [0]
          [0]
   [tt] = [1]
          [1]
   
         [X3]    [1 0 0 1][X3]   [1]
         [X2]    [0 0 0 0][X2]   [0]
   [U12]([X1]) = [0 0 0 0][X1] + [1]
         [X0]    [0 0 0 1][X0]   [0]
   
           [0]
           [0]
   [nil] = [0]
           [0]
   
        [X7]  [X3]    [1 0 1 0][X7]   [1 0 0 0][X3]   [1]
        [X6]  [X2]    [0 1 0 0][X6]   [0 1 0 0][X2]   [0]
   [__]([X5], [X1]) = [0 0 1 0][X5] + [0 0 1 0][X1] + [1]
        [X4]  [X0]    [0 0 0 1][X4]   [0 0 0 1][X0]   [0]
   
   
   Qed