Question

已知向量a=(2,t),b=(1,2),若t=t₁时,a∥b;t=t₂时,a⊥b,则(    )

A.t₁=-4,t₂=-1                               B.t₁=-4,t₂=1

C.t₁=4,t₂=-1                                D.t₁=4,t₂=1

Answer 1

答案:C

解析:t=t₁时,a∥b知2×2-t₁=0,t₁=4.

t=t₂时,a⊥b知2+2t₂=0,t₂=-1.