23.如圖,直線y=-x+n與x軸交于點(diǎn)A(3,0),與y軸交于點(diǎn)B,拋物線y=-x
2+bx+c經(jīng)過(guò)A,B.
(1)求拋物線解析式;
(2)E(m,0)是x軸上一動(dòng)點(diǎn),過(guò)點(diǎn)E作ED⊥x軸交于點(diǎn)E,交直線AB于點(diǎn)D,交拋物線于點(diǎn)P,連接PB.
①點(diǎn)E在線段OA上運(yùn)動(dòng),當(dāng)線段PD的長(zhǎng)度最大時(shí),求點(diǎn)P的坐標(biāo);
②點(diǎn)E在線段OA上運(yùn)動(dòng),若△PBD是等腰三角形時(shí),求點(diǎn)E的坐標(biāo).