contestada

Determine whether the function f : z × z → z is onto if
a.f(m,n)=m+n. b)f(m,n)=m2+n2.
c.f(m,n)=m.
d.f(m,n) = |n|.
e.f(m,n)=m−n.

Respuesta :

LammettHash
a. Yes; [tex]\mathbb Z[/tex] is closed under addition
b. No; [tex]m^2+n^2\ge0[/tex] for any integers [tex]m,n[/tex]
c. Yes; self-evident
d. No; similar to (b), because [tex]|n|\ge0[/tex] for any [tex]n\in\mathbb Z[/tex]
e. Yes; [tex]\mathbb Z[/tex] is closed under subtraction