题目

若代数式2x2﹣4x﹣5的值为7，则﹣x2+2x的值为（ ）A. 6 B. ﹣6 C. 1 D. ﹣1 答案：【答案】B【解析】根据题意得出2x2-4x-5=7，求出x2-2x=6，代入求出即可．解：根据题意得：2x2-4x-5=7， 2x2-4x=12， x2-2x=6， 所以-x2+2x=-6， 故选：B．We ate on the go more than ever before. Here are three health apps that can help you better manage your health when you pursue your dreams.(1)Doctors On DemandDoctors On Demand enables you to visit a doctor without ever leaving your home, helping you use a computer, tablet or smart phone to have a doctor video chat with you. The service will help you locate and connect you to licensed doctors, psychologists, pediatricians (儿科医生) and more. Fees can be paid with HAS&FSA. It costs $40 for 15 minutes with a doctor or $50 for 20 minutes with a psychologist.(2)Text4babyI’m a big fan of Text4baby for a few reasons. The free service for pregnant women and new moms works by sending text messages to your smart phone three times a week with information about how to have a healthy pregnancy and baby. And the messages are timed to the pregnant woman’s due date or the baby’s date of birth, sending tips that are relevant to where a mother is in her pregnancy or where a baby is in stages of development. Tips range from breastfeeding to car seat safety to reminders about exercise, nutrition and more. The service combines interactive text messages, an app, video and web content in English and Spanish. Sign up by texting BABY to 511-411 or by downloading the app.(3)RISERISE, an app available on iPhone(coming to Android in 2016), pairs you up with (与……绑定) a registered dietitian to improve your diet and reach health goals. You share photos of your meals and your exercise for the day with your coach, who then looks for areas where you can improve and gives advice, helps you set goals and is there to pat you on the back virtually(虚拟地) when you hit a milestone. What’s also great is that you can text as much as you want with your dietitian and there is no need to go into an office. Fees for this service range from $9 per month to $50 a month. There is a free 7-day trial so you can try it out for a week to see if it’s fit for you.1.How much will you pay if you have a video chat with your psychologist for an hour using Doctors On Demand?A. $50. B. $80. C. $100. D. $150.2.We can infer that the author is probably a ________.A. famous pediatrician B. software engineerC. pregnant woman or new mother D. registered dietitian3.What do you know about Text4baby?A. It is an app available only on iPhone.B. You can sign up by texting BABY to 511-411.C. People can’t use Text4baby for free.D. Text messages are sent in three languages.