how to simplify sums with constant subterms?

Dear list,


Maxima simplifies

sum(x, i, 1, n)

to

n * x

which is great.


But I have not figured out how to get Maxima to simplify

sum(x + a[i], i, 1, n)

to

n * x + sum(a[i], i, 1, n)


Any ideas/suggestions?


(This is in the context of Maximum Likelihood Estimation, where 
eventually I want to solve more complicated equations for x given n and 
a[i].)


Thanks,


Claude
-- 
https://mathr.co.uk