3

Problems(1)

Source: Bosnia and Herezegovina TST 2010 problem 3

f :\mathbb{Z}\mapsto\mathbb{Z}

a)

f(n) \cdot f(-n)=f(n^2)

n\in\mathbb{Z}

b)

f(m+n)=f(m)+f(n)+2mn

m,n\in\mathbb{Z}