题目

已知两向量a=(2λ,-1),b=(-2,1),λ∈R,       (1)若2a+b与a-2b平行,求λ的值；       (2)若2a+b与a-2b垂直,求λ的值.       答案：解析:∵a=(2λ,-1),b=(-2,1),       ∴2a+b=(4λ-2,-1),a-2b=(2λ+4,-3).       （1）当2a+b与a-2b平行时，有（4λ-2）·(-3)=(-1)·（2λ+4）,       ∴-12λ+6=-2λ-4.∴10λ=10.       ∴λ=1.       （2）当2a+b与a-2b垂直时，有（2a+b）·（a-2b）=0，       ∴（4λ-2）(2λ+4)+(-1)×(-3)=0,即8λ2+12λ-5=0.∴λ=.—Are you going to find a job or go on with your study to get a doctor’s degree? —I have had enough of ______ life. I want to find a job. A. ridiculous                B. appropriate             C. straightforward        D. academic