(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The problem is :

For the functions from N*N --> N, determine if the following functions are surjective:

f(a, b) = a + b

f(a, b) = ab(b+1)/2

2. Relevant equations

N is all natural numbers

3. The attempt at a solution

My problem is I know the definition of surjective, but I don't know what to do with f(a, b) because I've never seen this before. THanks for the help!

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# Homework Help: I never learned what f(a, b) means. . .

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