留坝县2006—2007学年度第二学期八年级数学期末试卷 一、选择题(每题3分,共30分): 1、计算:a2•a-4 的结果是                                             (     )   A.1         B. a-2      C.a          D. a-8  2、下列代数式                                 中,分式的个数有     (     ) A.1个       B.2个      C.3个       D.4个 3、化简 x4y3÷(xy)3  的正确结果是                                    (     ) A.x        B.x3                   C.xy          D. x2y 6、已知四边形ABCD中,AC⊥BD,E、F、G、H分别是AB、BC、CD、DA的中点,  则四边形EFGH是                                                (     )  A.菱形             B.矩形           C.正方形          D.梯形
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