问题 选择题
点P为△ABC所在平面内的点,若2
PA
+
PB
+
PC
=
0
AB
+
AC
=m
AP
,则实数m的值为(  )
A.2B.3C.4D.5
答案

AB
+
AC
=m
AP
,∴
PB
-
PA
+
PC
-
PA
=m
AP

2

PA
+
PB
+
PC
=
0
,∴
PB
+
PC
=-2
PA

-4

PA
=m
AP
,∴m
AP
=4
AP
,∴m=4.

故选C.

问答题
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