设集合A={a,b,c},B={-1,0,1},映射f:A→B满足f(a)-f(b)=f(c),求映射的个数
问题描述：
设集合A={a,b,c},B={-1,0,1},映射f:A→B满足f(a)-f(b)=f(c),求映射的个数
答
f:A->Bf(c)=1,f(a)= 1,f(b)=0f(c)=1,f(a)= 0,f(b)=-1f(c)=0,f(a)=0,f(b)=0f(c)=0,f(a)=-1,f(b)=-1 f(c)=0,f(a)=1,f(b)=1f(c)=-1,f(a)=0,f(b)=1f(c)=-1,f(a)=-1,f(b)=0total:7个