# [Maxima] wrong symbolic sum

Alexandros Droseltis ml-maxima at alex-droseltis.com
Sun Jul 26 08:04:37 CDT 2009

```Hello!

[Using Maxima 5.17.0 provided by the rpm 5.17.0-1.3 for openSuSE]

Please, have a look at this.

These sums are correct:

(%i27) sum(k, k, 1, 4);
(%o27)                                10
(%i28) sum(-k, k, -4, -1);
(%o28)                                10

Now check these two sums:

(%i1) simpsum: true;
(%o1)                                true
(%i2) sum(k, k, 1, a);
2
a  + a
(%o2)                               ------
2
(%i3) sum(-k, k, -a, -1);
Is  a  positive, negative, or zero?

p;
2
a  - a
(%o3)                               ------
2
(%i4) sum(-k, k, -a, -1);
Is  a  positive, negative, or zero?

n;
2
- a + (- a - 1)  - 1
(%o4)                        --------------------
2
(%i5) ratsimp(%);
2
a  + a
(%o5)                               ------
2

Should n't a positive "a" create the same result as %o2 and a negative
the empty sum, thus 0? Do I miss something?

Best Regards

Alexandros
```