问题
填空题
已知|
|
答案
∵|
+a
|=3，|b
-a
|=4b
∴|
+a
|2=b
2+a
2+b
•a
=9，①b
|
-a
|2=b
2+a
2-2b
•a
=16，②b
①-②得4
•a
=-7b
∴
•a
=-b 7 4
故答案为-7 4
搜题请搜索小程序“爱下问搜题”
已知|
|
∵|
+a
|=3，|b
-a
|=4b
∴|
+a
|2=b
2+a
2+b
•a
=9，①b
|
-a
|2=b
2+a
2-2b
•a
=16，②b
①-②得4
•a
=-7b
∴
•a
=-b 7 4
故答案为-7 4