题目

阅读理解In2016, China released guidelines forbidding weird(古怪的) construction,shifting their focus to the economic, green and beautiful. Now a newplan certainly fits the bill—Liuzhou Forest City, designed by the Italian firm StefanoBoeri Architetti, will be under construction in southern China.The175­hectare, self­contained neighborhood will contain more than 70 buildings—includinghomes, hospitals, hotels, schools and offices—all of which will be covered with40, 000 trees and almost a million plants. This is the first experiment of the urbanenvironment that's really trying to 18．已知函数f（x）=log${\;}_{\frac{1}{2}}$$\sqrt{-{x}^{2}+2x+8}$．（1）求f（x）的定义域；（2）求f（x）的值域．