F.5 A.Maths

let the point P is (x,y)
when the points which divide internally
x=(2*-1+-7)/(2+1)=-3
y=(2*-2+7)/(2+1)=1
Thus the point P is (-3,1)
when the point Q (x,y) which divide externally
PQ:QR=1:1
then
-1=(x-7)/2
x=5
-2=(7+y)/2
y=-3
so Q (5,-3)
then


2007-01-01 10:25:34 補充：
PQ:QR=1:1 應是PR:QR=1:1