# Reformulation

Obtaining a new formulation of a problem that is in some sense better, but equivalent to a given formulation. For example, consider the packing constraint: at most 1 element can be selected from $LaTeX: \textstyle \left \{1, \dots, n \right \}.$ Letting $LaTeX: x_j$ be the associated binary variable, the following formulations have the same feasibility region:
1. $LaTeX: x_i + x_j \le 1 \mbox{ for all } i < j, j=2, \dots,n;$
2. $LaTeX: x_1 + x_2 + \dots + x_n \le 1.$