y=x²+2（a-1）x+（a-1）²+a=x²+2ax-2x+a²-2a+1+a=X²+2（a-1）x+a²-a+1=X²+2（a-1）x+（a-1）²顶点横坐标：x=-b/2a =-a+1a＜0,-a＞0x＞1（顶点在第一或第四象限）再...