已知抛物线y2=2px(p>0)的焦点为F,点P1(x1,y1),P2(x2,y2),P3(x3,y3)在抛物线上,且2x2=x1+x3,则有(  ) A.|FP1|+|FP2|=|FP3| B.|FP1|2+|FP2|2=|FP3|2 C

问题描述:

已知抛物线y2=2px(p>0)的焦点为F,点P1(x1,y1),P2(x2,y2),P3(x3,y3)在抛物线上,且2x2=x1+x3,则有(  )
A. |FP1|+|FP2|=|FP3|
B. |FP1|2+|FP2|2=|FP3|2
C. 2|FP2|=|FP1|+|FP3|
D. |FP2|2=|FP1|•|FP3|

∵2x2=x1+x3
2(x2+

p
2
)=(x1+
p
2
)+(x3+
p
2
),
∴由抛物线定义可得2|FP2|=|FP1|+|FP3|
故选C.