Probability

圖片參考：http://img600.imageshack.us/img600/1962/66043585.jpg

For (b), it should be clearer to draw the diagram below and notice that the required area is the red region..
And it is much easier to calculate the triangle bounded by x=0, y=0 and the line x+y=2/3


圖片參考：http://img40.imageshack.us/img40/9061/37386935.jpg


圖片參考：http://img217.imageshack.us/img217/2181/89876706.jpg

Similar to (b), the red region is the required area.
圖片參考：http://img207.imageshack.us/img207/2746/19031317.jpg



圖片參考：http://img220.imageshack.us/img220/7128/15839982.jpg




2011-02-01 19:11:34 補充：
some mistake in (d) , it should be P(X

2011-02-01 19:11:55 補充：
some mistake in (d) , it should be P(X

2011-02-01 19:12:30 補充：
P( X, a, Y , b)

2011-02-01 19:12:44 補充：
P(X