在△ABC中,点P在BC上,且向量BP=2向量PC,点Q是AC的中点,若向量PA=（4,3）,向量PQ=（1,5）,则向量BC=

BP = 2PC
Q是AC的中点
=> AQ= QC = (1/2)AC
PA=(4,3),PQ=(1,5)
BC = BP+PC
=3PC
= 3(PA +AC)
= 3(PA + 2AQ)
= 3(PA + 2(-PA+ PQ) )
= 3((4,3) + 2(-3,2))
= 3((-2,7))
=(-6,21)