题目

阅读理解 Buildinga company website is one of the most important parts of creating a successful business.But designing a website can be time consuming and expensive. Web designers are difficultto work with, and even though you're paying them. There are cheaper ways to establishyour company online, and Wix.com stands out among them. Wix.comoffers free HTML5 and Flash website design that you can do on your own, withouthaving to pay for a pricey web designer. With unlimited space for as many pagesas you want, customized looks, photo galleries, and blog platform capabilities,social networking 如图，⊙O是以原点为圆心，2为半径的圆，点P是直线y=﹣x+4上的一点，过点P作⊙O的一条切线PQ，Q为切点，则切线长PQ的最小值为 ．