# C1 W2 practice quiz question 1

**URL:** <https://community.deeplearning.ai/t/c1-w2-practice-quiz-question-1/895165>\
**Category:** Linear Algebra for Machine Learning and Data Sc...\
**Tags:** week-module-1, dl-ai-learning-platform\
**Created:** [September 16, 2026, 11:31am UTC](https://community.deeplearning.ai/t/c1-w2-practice-quiz-question-1/895165 "2026-09-16T11:31:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Rachy](https://avatars.discourse-cdn.com/v4/letter/r/ecd19e/32.png) [@Rachy](https://community.deeplearning.ai/u/Rachy)\
**Post date:** [September 16, 2026, 11:31am UTC](https://community.deeplearning.ai/t/c1-w2-practice-quiz-question-1/895165/1 "2026-09-16T11:31:55Z")

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I think the scoring for Question 1 of the practice quiz (C1W2) is incorrect. I don’t want to post the answer here as that might be against forum rules.

Searched but couldn’t find this raised before.

This is quite an easy question as it’s just calculating the determinant. I also put the question into a AI which verified the answer I had was correct and that the system answer is wrong.

This is the Maths for ML course on the dl-ai-learning-platform.

Thanks

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**Author:** ![saou\_a](https://sea1.discourse-cdn.com/dlai/user_avatar/community.deeplearning.ai/saou_a/32/8429_2.png) [@saou\_a](https://community.deeplearning.ai/u/saou_a)\
**Post date:** [September 30, 2026, 1:02pm UTC](https://community.deeplearning.ai/t/c1-w2-practice-quiz-question-1/895165/2 "2026-09-30T13:02:37Z")

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Hi @Rachy ,

I believe Question 1 is correct. As a quick reminder, a matrix is **singular** when its determinant is zero, and **non-singular** when its determinant is non-zero. This is a common point of confusion for some learners.

@saou_a