Re: [中學] 向量
PA + 4PB + 5PC = AB
△ABC = 12
=> PA + 4PB + 5PC = PB - PA
=> 2PA + 3PB + 5PC = 0
PA' = 2PA
PB' = 3PB
PC' = 5PC
=> 6△PAB = 15△PBC = 10△PCA
=> △PAB : △PBC : △PCA = 5 : 2 : 3
=> △PAB = (5/10)△ABC = 6
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