21 Test file number 41

  21.1 Problem number 81
  21.2 Problem number 83
  21.3 Problem number 85

Test folder name:

test_cases/1_Algebraic_functions/1.2_Trinomial_products/1.2.2_Quartic/41_1.2.2.4-f_x-^m-d+e_x^2-^q-a+b_x^2+c_x^4-^p