# SymPy Simplify Problem with a lot of symbols

**URL:** <https://discourse.julialang.org/t/sympy-simplify-problem-with-a-lot-of-symbols/95486>\
**Category:** General Usage\
**Tags:** package\
**Created:** [March 3, 2023, 8:26am UTC](https://discourse.julialang.org/t/sympy-simplify-problem-with-a-lot-of-symbols/95486 "2023-03-03T08:26:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Freya\_the\_Goddess](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/freya_the_goddess/32/36835_2.png) [@Freya\_the\_Goddess](https://discourse.julialang.org/u/Freya_the_Goddess)\
**Post date:** [March 3, 2023, 8:26am UTC](https://discourse.julialang.org/t/sympy-simplify-problem-with-a-lot-of-symbols/95486/1 "2023-03-03T08:26:17Z")

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Hi all,

I just want to know why `simplify((a*x - b)*(a*x + b))` can’t become a^{2}x^{2} -b^{2} in Julia?

```julia
using SymPy
@syms x, a, b, c, t, u

c = (a^2 - b^2)/(2*a*b)
d = ((a*x -b)/(a*x+b))^c
f1(x) = log(d)

u = log(x^2 + x - 1)
f2(x) = integrate((cos(t)^2), (t, 1, u))

a1 = diff(f1(x),x)
a2 = diff(f2(x),x)

println("Computing symbolic derivative")
print("a. ", simplify(a1))
println("= ", a1(1))
print("b. ", simplify(a2))
println("= ", a2(1))

```

The point (a) should have the answer of 1, but instead of substituting 1 into `x` it substitutes 1 into `a`

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**Author:** ![fgerick](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/fgerick/32/13228_2.png) [@fgerick](https://discourse.julialang.org/u/fgerick)\
**Post date:** [March 3, 2023, 10:22am UTC](https://discourse.julialang.org/t/sympy-simplify-problem-with-a-lot-of-symbols/95486/2 "2023-03-03T10:22:20Z")

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```julia
julia> simplify(a1(x=>1))
1

```

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<div class="post-metadata">

**Author:** ![Freya\_the\_Goddess](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/freya_the_goddess/32/36835_2.png) [@Freya\_the\_Goddess](https://discourse.julialang.org/u/Freya_the_Goddess)\
**Post date:** [March 3, 2023, 11:06am UTC](https://discourse.julialang.org/t/sympy-simplify-problem-with-a-lot-of-symbols/95486/3 "2023-03-03T11:06:10Z")

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Thanks for this revelation. You are my savior!