YES(?,O(n^3))

Problem:
 a(b(a(x1))) -> a(a(b(b(a(a(x1))))))
 b(a(a(b(x1)))) -> b(a(b(x1)))

Proof:
 RT Transformation Processor:
  strict:
   a(b(a(x1))) -> a(a(b(b(a(a(x1))))))
   b(a(a(b(x1)))) -> b(a(b(x1)))
  weak:
   
  Matrix Interpretation Processor:
   dimension: 1
   interpretation:
    [b](x0) = x0,
    
    [a](x0) = x0 + 4
   orientation:
    a(b(a(x1))) = x1 + 8 >= x1 + 16 = a(a(b(b(a(a(x1))))))
    
    b(a(a(b(x1)))) = x1 + 8 >= x1 + 4 = b(a(b(x1)))
   problem:
    strict:
     a(b(a(x1))) -> a(a(b(b(a(a(x1))))))
    weak:
     b(a(a(b(x1)))) -> b(a(b(x1)))
   Matrix Interpretation Processor:
    dimension: 3
    interpretation:
               [1 0 2]     [0]
     [b](x0) = [0 0 6]x0 + [2]
               [0 0 0]     [0],
     
               [1 1 0]     [1]
     [a](x0) = [0 0 0]x0 + [0]
               [0 0 0]     [1]
    orientation:
                   [1 1 0]     [12]    [1 1 0]     [8]                       
     a(b(a(x1))) = [0 0 0]x1 + [0 ] >= [0 0 0]x1 + [0] = a(a(b(b(a(a(x1))))))
                   [0 0 0]     [1 ]    [0 0 0]     [1]                       
     
                      [1 0 8]     [6]    [1 0 8]     [5]              
     b(a(a(b(x1)))) = [0 0 0]x1 + [8] >= [0 0 0]x1 + [8] = b(a(b(x1)))
                      [0 0 0]     [0]    [0 0 0]     [0]              
    problem:
     strict:
      
     weak:
      a(b(a(x1))) -> a(a(b(b(a(a(x1))))))
      b(a(a(b(x1)))) -> b(a(b(x1)))
    Qed