# Algebrical equation

**URL:** <https://community.freefem.org/t/algebrical-equation/1124>\
**Category:** Feature Request\
**Created:** [July 28, 2021, 4:54pm UTC](https://community.freefem.org/t/algebrical-equation/1124 "2021-07-28T16:54:38Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Aicha](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Aicha](https://community.freefem.org/u/Aicha)\
**Post date:** [July 28, 2021, 4:54pm UTC](https://community.freefem.org/t/algebrical-equation/1124/1 "2021-07-28T16:54:38Z")

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Hi,  
can you help me please to resolve this question.  
I(x,t) is the solution of an variational solution system.  
To find I(x,t) we use

```auto
for (real t=0;t<T;t+=dt) {
system,
}

```

After this, how we can resolve the equation I(x,t)=0.5 for all t: we denote the solution x=x(t), and after this we calculate c(t)=x’(t) for all t.

Thank’s in advance .