问题
选择题
已知向量m=(λ+1,1),n=(λ+2,2),若(m+n)⊥(m-n),则λ等于( )
A．-4
B．-3
C．-2
D．-1
答案
答案：B
m+n=(2λ+3,3),
m-n=(-1,-1),
由题意知(m+n)·(m-n)=0,
即-(2λ+3)-3=0,
因此λ=-3.故选B.
搜题请搜索小程序“爱下问搜题”
已知向量m=(λ+1,1),n=(λ+2,2),若(m+n)⊥(m-n),则λ等于( )
A．-4
B．-3
C．-2
D．-1
答案：B
m+n=(2λ+3,3),
m-n=(-1,-1),
由题意知(m+n)·(m-n)=0,
即-(2λ+3)-3=0,
因此λ=-3.故选B.
| 短文改错。 | |
When my daughter Lee and his friends wanted to make planter boxes and sold them, I was glad they decided to earn money instead asking their parents for it, so I agreed to lend them hand. I gave them some carpentry (木工) lesson, and they all seemed capable (有能力) and carefully with my tools. Since they work behind the garage, a house is quieter than used to be. They are learning how to use money on a responsible (负责的) way, and I can tell that they feel quite be proud of themselves. | 1. ________ 2. ________ 3. ________ 4. ________ 5. ________ 6. ________ 7. ________ 8. ________ 9. ________ 10. ________ |