已知a>0，函数f(x)=ax2+bx+c，向量m→=2ax0+b,x0+1与向量n→=x02+1,2ax0+b垂直时，则下列选项的命题中为假命题的是（）

题干

已知a>0，函数f(x)=ax²+bx+c，向量m→=2ax0+b,x0+1与向量n→=x02+1,2ax0+b垂直时，则下列选项的命题中为假命题的是（）

A： $\exists x \in R, f (x) \leq f (x_{0})$

B： $\exists x \in R, f (x) \geq f (x_{0})$

C： $\forall x \in R, f (x) \leq f (x_{0})$

D： $\forall x \in R, f (x) \geq f (x_{0})$

上一题下一题 0.0难度选择题更新时间:2018-03-07 10:42:52

C

请你为下列的problems寻找合适的advice:

Problems	Advice
①Sometimes I get angry and shout at my friends. That makes them think I'm not friendly to them. ____	A. Let your parents know you will not be alone. Also, you can ask a teacher to talk to your parents about the after-school activities.
②In my teacher's eye s, I am a good student. Both my classmates and my parents also think so. No one knows what my problem is. I often feel worried about my schoolwork. ____	B. Don't worry. Even the great piano players have to practice a lot. Hard work and a lot of practice are the only ways if you want to become a good piano player.
③My parents never let me play computer games. They want me to study all the time and get good results. I feel unhappy. ____	C. When you feel angry, you should stop talking and walk away until you keep calm.
④ I want to take part in some after-school activities, but my parents think they are too dangerous and don't let me to go out alone. ____	D. Don't worry. Everybody worries about their schoolwork, even the top students. Find a hobby or a sport to help you relax.
⑤My mother asks me to have piano lessons. She makes me practise two hours a day. I really try my best, but I just can't play well. ____	E. Tell your parents that many children play computer games and do well at school, too. Ask them to let you play computer games for a short time on weekends.