16 Test file number 26

  16.1 Problem number 31
  16.2 Problem number 61
  16.3 Problem number 134
  16.4 Problem number 139
  16.5 Problem number 291
  16.6 Problem number 292

Test folder name:

test_cases/1_Algebraic_functions/1.1_Binomial_products/1.1.3_General/26_1.1.3.3-a+b_x^n-^p-c+d_x^n-^q