问题补充:
单选题已知A={a,b,c},B={-1,0,1},函数f:A→B满足f(a)+f(b)+f(c)=0,则这样的函数f(x)有A.4个B.6个C.7个D.8个
答案:
C解析对f(a),f(b),f(c)的值分类讨论.当f(a)=-1时,f(b)=0,f(c)=1或f(b)=1,f(c)=0,即此时满足条件的函数有2个;当f(a)=0时,f(b)=-1,f(c)=1或f(b)=1,f(c)=-1或f(b)=0,f(c)=0,即此时满足条件的函数有3个;当f(a)=1时,f(b)=0,f(c)=-1或f(b)=-1,f(c)=0,即此时满足条件的函数有2个.综上所得,满足条件的函数共有2+3+2=7(个).故选C.