# Disputed VLQ flag for an LP answer

Update: answer mod-deleted. This is not a VLQ, but it is an NAA. Please see my answer for explanations.

In LP-problem simplex with 3 variables, the question asker asks for "simplex calculations". Anyone who knows some introductory will understand that this stands for "simplex algorithm", which is an algorithm iterating through the extreme points of the (convex) set of possible solutions. Obviously, he/she is expecting a solution with a simplex tableau.

The main goal of such kind of exercises is to get students know the simplex algorithm through practising it (on paper). This is the basics just like warm-up exercises for further topics in LP such as sensitivity analysis. To assess student's understanding of the simplex algorithm in a two-hour exam, teachers may set up an "easy" problem like this and ask students to solve it using the algorithm, so that students can verify their final results found by the algorithm through comparing them with those found by directly solving the system.

The answer in this question shows no simplex iteration, so it's VLQ and NAA. I used the former flag, so that it entered into LQ review. Unluckily, only one reviewer has noticed this. The other reviewers have never created a post in . Despite my comment at the bottom, they have voted "Looks OK". As a result, I've used the second flag. Please delete this answer.

• I understand how you can feel that an Answer to such a linear programming problem is unsatisfactory, but that is at some distance from what we consider "very low quality". If you read the fuller description, it suggests that the post may be so poor that it is beyond salvaging with recommended edits. In this case I'd recommend that you post an Answer you consider satisfactory (unless one has already been posted by someone else). Feb 13, 2019 at 3:24
• @hardmath I've posted a suggestion to the answer instead. Thanks for feedback. I've posted another meta question about another LQ review of linear programming answer. Perhaps you can help. I'm going to self-answer this question with your comments. Feb 13, 2019 at 10:12

However, it's an NAA since the OP "need[s] to solve [the problem] using simplex calculations". To start with, OP is expecting a transformation like those in What to do about equality constraints in the Simplex Tableau method or https://stackoverflow.com/q/17289032/3184351. The key idea of this trick should be so easy that even a primary school kid can understand without any problem. However, the answer (to $$AX = b$$) is calculated by direct matrix inversion ($$X = A^{-1}b$$). This is not "simplex calculations", so it's not respecting the requirements in the question, and thus an NAA.