Author 
Comment/Response 
M Belevich

09/10/11 12:06pm
Hello,
please help me with three little problems.
1) How to cancel common factors in expressions which include Sum[...] and Integrate[...]? My particular expression is like this one
Sum[a*f[k], {k, 0, K}]/a
Simplify and FullSimplify don't work.
2) How to simplify the following expression with DiracDelta
Sum[DiracDelta[j  k]*f[k], {k, K, K}]
and to get f[j].
3) How to substitute Integrate[Sum[...]] for Sum[Integrate[...]] in this simple example
Integrate[Sum[f[k,x],{k,0,K}],{x,a,b}]
in order to obtain
Sum[Integrate[f[k,x],{x,a,b}],{k,0,K}]
I would be grateful for any help.
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