A={1,2,3},B={4,5,6}
f:A->B
f(1) =4
這樣的映射有 = 2^2 = 4個"這樣的映射有 = 2^2 = 4個"這個怎么來的呢？請分析一下，謝謝！應(yīng)該是3^2 = 9個f(1) =4, f(2)= 4 f(3)= 4 or 5 or 63個f(1) =4, f(2)= 5 f(3)= 4 or 5 or 63個f(1) =4, f(2)= 6 f(3)= 4 or 5 or 63個