# Properties of exponentials - symbolic algebra

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Luca Lazzizzera on 16 Apr 2021
Edited: Luca Lazzizzera on 18 Apr 2021
Hello all,
I am experiencing problems with the properties of exponentials, in particular when the exponent is a symbolic variable.
For example, if I set
syms x y
and I want to evaluate
exp(x)*exp(y)
is there a way of having the result the exponential with the sum of exponents
exp(x+y)
Notice that it does work for one variable only, i.e. exp(x)*exp(x)=exp(2*x)
Thank you very much!

Mischa Kim on 16 Apr 2021
Hi Luca, use
syms x y
z = simplify(exp(x)*exp(y))
z = Luca Lazzizzera on 18 Apr 2021
It works as long as the variables are just "x" and "y", but it does not always work, in particular if the product of exponentials is a term in a sum with other terms like exp(x)
for example 6*exp(x) + 5*exp(-x)*exp(y) + 4*exp(-2*y)*exp(x)
does not get simplified for some reason (I have to compute partition functions with many summed terms like this, many more than 3).
Is there any other more powerful/reliable way?
Thank you again