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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.

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  • $\begingroup$ 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). $\endgroup$ – hardmath Feb 13 at 3:24
  • $\begingroup$ @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. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Feb 13 at 10:12
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Based on hardmath's comment, I am posting a partial answer here about VLQ.

Based on The limits to a Very Low Quality answer, the VLQ flag should be used when the content is unsalvageable and it can't be improved through edits. Typical examples are poorly formatted code and unreadable mess. The review target isn't a VLQ since it's readable and contains (sound and valid) mathematical content.

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.

The question asker has spotted out the missing slack variables in the answer, and he/she is kind and patient enough to post a comment and wait for the answerer's clarifications. However, the answerer fails to respond to asker's question :(

Flagging an answer with either VLQ or NAA will send it to the LQ review queue in sooner or later, so the question of why the review target has passed linked review remains unresolved.

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