Hi enriquestefanini,

well, by the definition of a function

, and you have g

G,

then there is at most

**one** image f(g) = h

H (there cannot be two distinct elements of H being

the image of g, since this would be in contrary to the definition of a function).

So if you have at least two elements in the image of f, e.g.

, then

you have at least two different elements of G. Then it follows that M cannot be 1 alone, since if it was,

there would be only

**one** element in f(M).

Further, the image f(N)

H.

Is that clear to you now?