问题
解答题
设
(1)若
(2)若
|
答案
∵
,e1
是两个相互垂直的单位向量,e2
∴
=-(2a
+e1
)=(-2,-1),e2
=b
-λe1
=(1,-λ),e2
(1)∵
∥a
,b
∴(-2)•(-λ)-1•(-1)=0,解得 λ=-
.1 2
(2)∵
⊥a
,∴b
•a
=0,即 (-2)•1+(-1)•(-λ)=0,解得 λ=2.b
设
(1)若
(2)若
|
∵
,e1
是两个相互垂直的单位向量,e2
∴
=-(2a
+e1
)=(-2,-1),e2
=b
-λe1
=(1,-λ),e2
(1)∵
∥a
,b
∴(-2)•(-λ)-1•(-1)=0,解得 λ=-
.1 2
(2)∵
⊥a
,∴b
•a
=0,即 (-2)•1+(-1)•(-λ)=0,解得 λ=2.b