【简答题】在等差数列{a n }中,a 1 =1,a 5 =9,在数列{b n }中,b 1 =2,且b n =2b n-1 -1,(n≥2) (1)求数列{a n }和{b n }的通项公式; (2)设 T n = a 1 b 1 -1 + a 2 b 2 - 1 + a 3 b 3 -1 +…+ a n b n -1 ,求T n .
【单选题】驾驶机动上在道路上违反交通安全法的行为,属什么行为( )。
【单选题】驾驶机动车在道路上违反交通安全法的行为,属( )行为。
【单选题】在等比数列{a n }中, a 1 + a 2 +…+ a 5 =27, 1 a 1 + 1 a 2 +…+ 1 a 5 =3 ,则a 3 =( )
【简答题】Food waste in less-developed countries happens mainly at the producers end.
【单选题】老年人要多吃新鲜瓜果蔬菜,每天不少于多少克( )
【单选题】China’s New Food Act provides for a food recall system to producers have to stop production their food isn’t up to standards.
【单选题】老年人要多吃新鲜瓜果、绿叶蔬菜,每天不少于()。