# Coupled high order PDE

**URL:** <https://community.freefem.org/t/coupled-high-order-pde/577>\
**Category:** General Discussion\
**Created:** [September 8, 2020, 6:38pm UTC](https://community.freefem.org/t/coupled-high-order-pde/577 "2020-09-08T18:38:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![alexwems1](https://avatars.discourse-cdn.com/v4/letter/a/5e9695/32.png) [@alexwems1](https://community.freefem.org/u/alexwems1)\
**Post date:** [September 8, 2020, 6:38pm UTC](https://community.freefem.org/t/coupled-high-order-pde/577/1 "2020-09-08T18:38:17Z")

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Hi, Can I have some help to solve this PDEs system. I am having a lot of troubles with this.  
This are the equations:  
! ![Captura1](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/1X/aaea8a24eb55aa67b30016acc98bb2c7f437b2bd.jpeg)  
If you wanna see more about, you can watch this document. [https://docs.google.com/document/d/1ix\_8FZYo\_AkyqzrmUip3VybtI8tlFUrzcmqOP6z94Xc/edit?usp=sharing](https://docs.google.com/document/d/1ix_8FZYo_AkyqzrmUip3VybtI8tlFUrzcmqOP6z94Xc/edit?usp=sharing)

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**Author:** ![frederichecht](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/frederichecht/32/15_2.png) [@frederichecht](https://community.freefem.org/u/frederichecht)\
**Post date:** [September 22, 2020, 9:45am UTC](https://community.freefem.org/t/coupled-high-order-pde/577/2 "2020-09-22T09:45:31Z")

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I am sorry, but the system is order 4, in 1d with no variational form,  
you have to work a solve.

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<div class="post-metadata">

**Author:** ![alexwems1](https://avatars.discourse-cdn.com/v4/letter/a/5e9695/32.png) [@alexwems1](https://community.freefem.org/u/alexwems1)\
**Post date:** [September 23, 2020, 1:45am UTC](https://community.freefem.org/t/coupled-high-order-pde/577/3 "2020-09-23T01:45:25Z")

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There is a way to transform this system in to a weak form?