Question

下列每組中各點(diǎn)共線的有(    )

①A(1,2),B(-3,-4),C(2,3.5) 

②A(-1,2),B(0.5,0),C(5,-6) 

③A(9,1),B(1,-3),C(8,0.5) 

④A(-2,-3),B(2,1),C(1,4),D(-7,-4)

A.4組              B.3組                   C.2組               D.1組

Answer 1

解析:①中=-4,②中=,③中=8,均有A,B,C三點(diǎn)共線,而④中, =(4,4),=(3,7),有4×7-3×4≠0,∴,即A,B,C三點(diǎn)不共線,更談不上A,B,C,D四點(diǎn)共線.

答案:B