（1）由题意得：x+1/x-2≥0且x-2≠0
解得：x≤-1或x＞2
∴A={x/x≤-1或x＞2}
(x+y)*6/2-(x+y)*6/2=12 3x+3y-3x+3y=12 6y=12 y=2答：梯形的下底是2.
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