A:氟乙烯和全氟异丙烯
B:1,1二氟乙烯和全氟丙烯
C:1三氟甲基1,3丁二烯
D:全氟异戊二烯
In my driving lesson, I learned a traffic rule that at no time _____ parked in a manner which will block emergency service.
设函数f(x)=x2+ax+b,a,b∈R.
(1)若a+b=3,当x∈1,2时,f(x)≥0恒成立,求实数a的取值范围;
(2)是否存在实数对(a,b),使得不等式|f(x)|>2在区间1,5上无解,若存在,试求出所有满足条件的实数对(a,b);若不存在,请说明理由.