# Week 4 assignment part 1 Exercise 9 - L\_model\_backward

**URL:** <https://community.deeplearning.ai/t/week-4-assignment-part-1-exercise-9-l-model-backward/23061>\
**Category:** Neural Networks and Deep Learning\
**Tags:** coursera-platform\
**Created:** [July 24, 2021, 2:38pm UTC](https://community.deeplearning.ai/t/week-4-assignment-part-1-exercise-9-l-model-backward/23061 "2021-07-24T14:38:03Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Arjun\_rao\_k](https://avatars.discourse-cdn.com/v4/letter/a/8491ac/32.png) [@Arjun\_rao\_k](https://community.deeplearning.ai/u/Arjun_rao_k)\
**Post date:** [July 24, 2021, 2:38pm UTC](https://community.deeplearning.ai/t/week-4-assignment-part-1-exercise-9-l-model-backward/23061/1 "2021-07-24T14:38:03Z")

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![image](https://global.discourse-cdn.com/dlai/original/2X/3/360e654267bc0d737a5286ac9d54903b0f0caef7.png)

why dA1 is not working.

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**Author:** ![albertovilla](https://sea1.discourse-cdn.com/dlai/user_avatar/community.deeplearning.ai/albertovilla/32/4530_2.png) [@albertovilla](https://community.deeplearning.ai/u/albertovilla)\
**Post date:** [July 25, 2021, 9:02am UTC](https://community.deeplearning.ai/t/week-4-assignment-part-1-exercise-9-l-model-backward/23061/2 "2021-07-25T09:02:41Z")

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Hi,

That error indicates you have not defined `dA1`, I would suggest you to check the code where `grads` is created.

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**Author:** ![MoHassan](https://sea1.discourse-cdn.com/dlai/user_avatar/community.deeplearning.ai/mohassan/32/7566_2.png) [@MoHassan](https://community.deeplearning.ai/u/MoHassan)\
**Post date:** [August 3, 2021, 7:19am UTC](https://community.deeplearning.ai/t/week-4-assignment-part-1-exercise-9-l-model-backward/23061/3 "2021-08-03T07:19:02Z")

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@albertovilla  
Hello, I 've got the same error without outputting dA0, and I 'm following the instructions in the code comments.