Determine whether f : Z × Z → Z is onto if a) f (m, n) = 2m − n. b) f (m, n) = m² − n²

[Dhanalakshmi]

Determine whether f : Z × Z → Z is onto if
a) f (m, n) = 2m − n.
b) f (m, n) = m² − n².
c) f (m, n) = m + n + 1.
d) f (m, n) = |m| − |n|.
e) f (m, n) = m² − 4.