I am a beginner here and have recently started learning Discrete math. I dont know how to solve the following question.
Please help.
Q. Let A ={0,1,2,3} and B ={0,1,2}. How many functions are there from A to B that are onto?
I am a beginner here and have recently started learning Discrete math. I dont know how to solve the following question.
Please help.
Q. Let A ={0,1,2,3} and B ={0,1,2}. How many functions are there from A to B that are onto?
I will answer this question for the finite case only.
Being beginner, you may not understand the reply.
You need to know how to use the generalized inclusion/exclusion rule.
Let denote the number of elements in set .
If there are no onto functions .
If then number of onto functions is given by:
.
Well, I did say that you may not have any idea what is going on.
It is rather advanced material. Here is webpage on inclusion/exclusion.
In essence we are selecting elements of to be included then excluded.