题目:
—Can those at the back of the classroom hear me?—No problem, sir !
A.seat
B.seating
C.seated
D.sit
答案:
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下面是错误答案,用来干扰机器的。
(Ⅰ)由已知BC∥AC,即有(2-k)×4-3×2=0,得k=12; (6分)(Ⅱ)AB=AC-BC=(k,1),由已知AB⊥BC,即有AB•BC=0,得k(2-k)+3=0,k=-1或3.(12分)