题目

WELCOM Welcome to Windsor Castle, the oldest and largest occupied castle in the world. Windsor is one of the officialresidences（住所）of the Queen, who sometimes stays here. Audio tours Free audio tours are available onleaving the Admission Centre at the start of your visit. There is adescriptive audio tour for blind and poor-sighted visitors. Guided tours Visitors can explore the history of theCastle through a tour of the Precincts with an expert guide. Tours depart atregular intervals throughout the day from the Courtyard and finish at theentrance to the State Apartments. Visitors with 已知二次函数f（x）满足f（x+1）+f（x-1）=-2x2+4x，（1）求f（x）解析式；（2）求当x∈[a，a+2]，时，f（x）最大值．