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September 11th, 2017, 03:30 PM  #1 
Newbie Joined: Jan 2017 From: USA Posts: 11 Thanks: 0  Need help with partial function problem.
It's a problem from discrete math, not calculus. I don't know where else to post it though. Can someone please help me understand what exactly this question is asking me to do? "Show that a partial function from A to B can be viewed as a function f* from A to B U {u}, where u is not an element of B and f*(a) = {f(a) if a belongs to the domain of definition of f, OR u if f is undefined at a}" I can see that it makes sense, but I don't know how to show that, or how to solve this problem. Please help. Last edited by skipjack; September 11th, 2017 at 04:40 PM. 
September 11th, 2017, 05:01 PM  #2 
Global Moderator Joined: Dec 2006 Posts: 17,919 Thanks: 1385 
It doesn't make sense to me  mainly because it's vague. What does "viewed as" mean? It would seem that the partial function is named f, but the problem doesn't explicitly say so  it just refers to f without explaining what f is. For it to make a little sense, A and B need to be sets, but the problem doesn't explicitly state that they are. If they are, a partial function from A to B is simply a function from C to B, where C is a subset of A. This definition doesn't require that C is known. Without a definition of "viewed as", it's impossible to make any further progress with this problem. 
September 11th, 2017, 05:16 PM  #3  
Newbie Joined: Jan 2017 From: USA Posts: 11 Thanks: 0  Quote:
 
September 11th, 2017, 05:24 PM  #4 
Global Moderator Joined: May 2007 Posts: 6,306 Thanks: 525  

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