设抛物线上点A横坐标是a则a²=-2pyy=-a²/2p所以A(a,-a²/2p)距离=|3a-4a²/2p-8|=√(3²+4²)=|2a²/p-3a+8|/5=|(2/p)(a-3p/4)²-9p/8+8|/5最小=1则|(2/p)(a-3p/4)²-9p/8+8|...