题一A={1,2}B={3,4,5,6,7,}f:A→B若x+f(x)为偶数x∈A则f:A→B共多少个?
题二f:x→y=-x²+2x是实数集M到实数集N的映射.若P∈N但P在M中无原像则P范围为多少?