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Was exploring quadratic programming optimization and for two types of problems the answers seemed to always equal.

Problem 1:

  • Minimize $\tfrac{1}{2} \mathbf{x}^T Q\mathbf{x}$
  • Subject to $ A \mathbf{x} = \mathbf{b} $ and $\mathbf{x}>0$
  • $ Q = n \mathbf{I}_{(n,n)} - \mathbf{1}_{(n,n)}$
  • Call the solution $\widehat{\mathbf{x}}$

Problem 2:

  • Define $ S_R = R \mathbf{I}_{(n,n)} - \mathbf{1}_{(n,n)}$ for scalar $0<R<n$
  • Maximum R such that there exist a non-trivial solution $\mathbf{x}$ such that $\tfrac{1}{2} \mathbf{x}^T S_R\mathbf{x}=0$
  • Subject to $ A \mathbf{x} = \mathbf{b} $ and $\mathbf{x}>0$ (same as Problem 1)
  • Call the solution of $\mathbf{x}$ for the maximum R to be $\widetilde{\mathbf{x}}$

Is it always true that $\widehat{\mathbf{x}}$ = $\widetilde{\mathbf{x}}$ ?

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