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.
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