数学向量提一道

3^2+(2+k)^2<=25
k<=2且>=-6

|a+b|?
a+b=(3,k+2)
所以
9+ (k+2)^2<=25
(k+2)^2<=9

-4<=k+2<=4
-6<=k<=2

向量a+b=(3,2+k)
绝对值不超过5,即a+b模的平方小于等于25
3^2+(2+k)^2<=25
9+4+4k+k^2<=25
k^2+4k-12<=0
(k+6)(k-2)<=0
则k的范围是大于等于-6,或小于等于2