y=ax^2-5ax+4,對(duì)稱(chēng)軸方程為X=-b/2a=5/2,
點(diǎn)C坐標(biāo)為(0,4),
BC//x軸,AC=BC,
Y=4,即有4=ax^2-5ax,
ax^2-5ax=0,
a1+x2=5,X1*X2=0,
而|X2-X1|=|BC|,
(X1+X2)^2-4X1*X2=BC^2,
BC=5,AC=5,
則點(diǎn)B坐標(biāo)為(5,4),點(diǎn)A坐標(biāo)為(3,0),
0=a*9-5*a*3+4,
a=2/3,
AB的中點(diǎn)坐標(biāo)為X=(5+3)/2=4,Y=4/2=2,
點(diǎn)AB的中點(diǎn)在直線PC上,
設(shè),PC的直線方程為Y=KX+4,則有
2=4*K+4,K=-1/2.
PA=PB,
PC的直線方程為Y=-1/2X+4,
X=5/2,代入Y=-1/2X+4,得Y=-1/2*(5/2)+4=11/4.
則點(diǎn)P的坐標(biāo)為(5/2,11/4).