3.如圖,點(diǎn)P在y軸上,⊙P交x軸于A,B兩點(diǎn),連接AP并延長(zhǎng)交⊙P于C點(diǎn),過(guò)點(diǎn)
C的直線y=-2x+b交x軸于點(diǎn)D,交y軸于點(diǎn)E,且⊙P的半徑為
,AB=4.
(1)求點(diǎn)P,點(diǎn)C的坐標(biāo);
(2)求證:CD是⊙P的切線;
(3)若二次函數(shù)y=-
x
2+mx+n的圖象經(jīng)過(guò)A,C兩點(diǎn),求這個(gè)二次函數(shù)的解析式,并寫(xiě)出使函數(shù)值大于一次函數(shù)y=-2x+b值的x的取值范圍.