# Trying to analytically solve a simple linear system

**URL:** <https://discourse.julialang.org/t/trying-to-analytically-solve-a-simple-linear-system/68645>\
**Category:** New to Julia\
**Tags:** linearalgebra, symbolics\
**Created:** [September 23, 2021, 8:00pm UTC](https://discourse.julialang.org/t/trying-to-analytically-solve-a-simple-linear-system/68645 "2021-09-23T20:00:46Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![hdcpereira](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/hdcpereira/32/28705_2.png) [@hdcpereira](https://discourse.julialang.org/u/hdcpereira)\
**Post date:** [September 23, 2021, 8:00pm UTC](https://discourse.julialang.org/t/trying-to-analytically-solve-a-simple-linear-system/68645/1 "2021-09-23T20:00:46Z")

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Hello there. I’m trying to solve the following system:

```julia
i1 = i2 + i3;
V = i1*r1 + i2*r2;
V = i1*r1 + i3*r3;

```

Which is fairly simple to solve, so I tried to use Symbolics.jl to do so. I’ve done the following:

```julia
using Symbolics

@variables r1, r2, r3;
@variables V;
@variables i1, i2, i3;

eq1 = Equation(i1, i2 + i3)
eq2 = Equation(E1, i1*r1 + i2*r2)
eq3 = Equation(E1, i1*r1 + i3*r3)

Symbolics.solve_for([eq1, eq2, eq3],[i1, i2, i3])

```

But it fails to solve, returning me the following error:

```julia
LoadError: AssertionError: i1 == i2
AssertionError: i1 == i2

```

Am I using symbolics.jl wrong? or maybe theres a better library for doing so.

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<div class="post-metadata">

**Author:** ![EvoArt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/evoart/32/25357_2.png) [@EvoArt](https://discourse.julialang.org/u/EvoArt)\
**Post date:** [September 24, 2021, 1:33pm UTC](https://discourse.julialang.org/t/trying-to-analytically-solve-a-simple-linear-system/68645/2 "2021-09-24T13:33:06Z")

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Is E1 supposed to be declared as a variable?

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<div class="post-metadata">

**Author:** ![VivMendes](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vivmendes/32/16477_2.png) [@VivMendes](https://discourse.julialang.org/u/VivMendes)\
**Post date:** [September 24, 2021, 1:58pm UTC](https://discourse.julialang.org/t/trying-to-analytically-solve-a-simple-linear-system/68645/3 "2021-09-24T13:58:28Z")

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Hi,  
You are trying to solve an undetermined system. As its stands, it is impossible to get a solution out of it. Your system can be reduced to two equations and four unknowns (`i1,i2,i3,r2`). That is why you are getting that error: the package is trying to help you.