tanotes2 - CO 350 Linear Optimization (Spring 2009) TAs...

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CO 350 Linear Optimization (Spring 2009) TA’s comments for Assignment 2 Q1, Q2: Most students got close but not many received full marks. A few common errors: Not moving all constants in a constraint to the right hand side (e.g. - (4 - 2 x 3 ) - x 2 ≤ - 1). Not including non-negativity constraints. For example, in Q2, although it’s blatantly clear that x 3 can only take positive values, it is still required to include x 3 0 to make it standard inequality form. Forgetting to flip the sign of the RHS when reversing the sign of a constraint (e.g. turning x 1 + x 2 1 into - x 1 - x 2 1). In Q2, quite a few students took the constraint x 2 0 as a “real” constraint, and treated x 2 as a free variable. They substituted x 2 = u 2 - v 2 and ended up capturing x 2 0 by - u 2 + v 2 0 ,u 2 0 ,v 2 0. While this is not “wrong”, it’s unnecessary and inefficient in practice. Q3:
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tanotes2 - CO 350 Linear Optimization (Spring 2009) TAs...

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