Revision history [back]

I'm trying to expand $(q + 1)/(q - 3)$ at $q=\infty$. This doesn't work:

sage: f=(q + 1)/(q - 3)
sage: f.series(q==infinity,3)
Order(-Infinity)

This also doesn't:

sage: f.subs(q==1/q).series(q==0,3).subs(q==1/q)
-1/2/q - 1/2

(the value is wrong, it should be 1 as $q$ goes to infinity, not $-1/2$).

This works:

sage: f.subs(q==1/q).simplify_rational().series(q==0,3).subs(q==1/q)
4/q + 12/q^2 + 1

But is not very friendly. Any ideas?

I'm trying to expand $(q + 1)/(q - 3)$ at $q=\infty$. This doesn't work:

sage: f=(q + 1)/(q - 3)
sage: f.series(q==infinity,3)
Order(-Infinity)

This also doesn't:

sage: f.subs(q==1/q).series(q==0,3).subs(q==1/q)
-1/2/q - 1/2

(the value is wrong, it should be 1 as $q$ goes to infinity, not $-1/2$).

This works:

sage: f.subs(q==1/q).simplify_rational().series(q==0,3).subs(q==1/q)
4/q + 12/q^2 + 1

But is not very friendly. Any ideas?