求问2到数学

李大纹要坚强

1. Pick two numbers from set 1 and set 2 separately, set 1 {1,2,3,4}, set 2 {4,1,7,8}, what is the probability of getting at least one 4 in the choice ?

答案是7/16


2. C D = 6 , p o i n t A l i e s o n l i n e C D , p o i n t B i s n o t o n l i n e C D , w h e r e 1 ≤ A B < 2 , w h a t ’s
the range of area of triangle BCD ?


[img]blob:https://forum.chasedream.com/9c2e23a3-50ce-4c3f-929b-35e7b1ce1099[/img]
答案是：6

请指教～～谢谢