6个大小相同的小球分别标有数字1,1,1,2,2,2,把它们放在一个盒子里,从中任意摸出两个小球,它们所标有的数字分别为m,n,记S=m+n. (I)设“S=2”为事件A,求事件A发生的概率; (II)记S max 为S的最大值,S min 为S的最小值,若a∈[0,S max ],b∈[S min ,3],设“x 2 +2ax+b 2 ≥0恒成立”为事件B,求事件B发生的概率.
【简答题】用方框中所给词完成句子。 took part in, hungry, improve, population, describe, strict with, tidy, introduce, learn from, practice 1. The best way to ______ your English is to join an English club. ...
【简答题】用方框中所给的词完成短文。 service, popular, survey, best, think, what, play, friendliest, and,delicious What do students 1 about fast-food restaurants in our city? We did a 2 of the students in our school last we...
【简答题】用方框中所给单词完成句子。 really , cousin , traffic , cost , exciting ,comedies ,meeting , easier, fan , ticket 1. We can't go to the concert without a____. 2. He's a real football____so is his father. 3. It's _...
【简答题】用方框中所给词的适当形式完成句子。 pronounce, different, mistake, face Tom came from the south of the country. In our language class, our teacher asked him ___ 1 __the word but his __ 2 ___ was strange. We all...