A、<img width='22' height='36' src='/s/tiw/p3/UpLoadImage/2013-05-07/0b957743-b903-4057-8ac2-e997ad1c3f60.png'>
B、<img width='14' height='36' src='/s/tiw/p3/UpLoadImage/2013-05-07/7eea6812-41de-4c5c-85bd-361d94adc771.png'>
C、<img width='22' height='38' src='/s/tiw/p3/UpLoadImage/2013-05-07/121cf079-c4c3-479f-98fb-5aa456abb139.png'>
D、<img width='14' height='38' src='/s/tiw/p3/UpLoadImage/2013-05-07/99ba09da-d485-49e3-b48e-dc4711c4a477.png'>
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试题解析
因为
所以(3,x)·(7,12)=0,即21+12x=0,解此方程得x=
.