Question

已知二次函数y=ax2+2x+3图象与x轴交于点A,点B(点B在X轴的正半轴上),与Y轴交于点C,其顶点为D,直线DC的

Answer 1

(1)∵y=ax²+2x+3∴C﹙0,3﹚又∵tan∠OBC=1∴OB=OC=3∴B﹙3,0﹚又∵点B在y=ax²+2x+3上∴a=-1∴y=-x²+2x+3=-(x-1)²+4∴A(-1,0),D(1,4)又∵点D在y=kx+3上∴k=1(2)存在.∵OB=3,OC=3,由勾股定理得：B...