A jar contains only x black balls and y white balls. One ball is drawn randomly from the jar and is not replaced. A second ball is then drawn randomly from the jar. What is the probability that the first ball drawn is black and the second ball drawn is white?
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A$$[\frac{x}{x+y}][\frac{x}{x+y}]$$
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B$$[\frac{x}{x+y}][\frac{x-1}{x+y-1}]$$
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C$$\frac{xy}{x+y}$$
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D$$[\frac{x-1}{x+y}][\frac{y-1}{x+y}]$$
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E$$[\frac{x}{x+y}][\frac{y}{x+y-1}]$$
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正确答案: E