题目

Singapore’s public transport system (公共交通系统) is one of the best in the world, so you should have no problem finding your way around like a local (当地人). There are three main forms of public transport that you would find in any other major city—trains, buses and taxis. TRAINS Trains run from 6 a.m. to midnight. Single trip tickets start at 80 cents. If you buy an EZ-Link card for $15, you can ride the trains and buses all you like. If you need more information, just call TransitLink on 1800 767 4333. BUSES There are several bus services in Singapore and fares (车费) start已知不等式ax2+bx+a＜0（ab＞0）的解集是空集，则a2+b2-2b的取值范围是     ．