问题
选择题
下列各组向量中, 向量a , b, c 共面的一组是 ( )
A．a =" (" 4, 2, 1 ), b =" (–1," 2 , 2 ), c =" (" –1, 1 ; 5 ).
B． a =" (" 1, 2, –3 ), b =" (–2," –4 , 6 ) , c =" (" 1, 0 ,5 ).
C．a =" (" 0, 0, 1 ), b =" (–1," 0 , 0 ), c =" (" 0, –1 ; 0 ).
D．a =" (" –2, 3, 1 ), b =" (3," –2 , –2 ), c =" (" –1, 0 ; 2 ).
答案
答案：B
对于选项B，∵(–2, –4 , 6 )=" -2" ( 1, 2, –3 )，∴b =-2a，即向量a 与b 共线，所以a =" (" 1, 2, –3 ), b =" (–2," –4 , 6 ) , c =" (" 1, 0 ,5 )共面，故选B
