AB=|2+2|=4
S(PAB)=1/2AB*|Xp|=1/2*4*|Xp|=6
所以,|X p|=3.
即Xp=-3,Yp=-1/(-3)=1/3
或Xp=3,Yp=-1/3
即P坐标是(-3,1/3)或(3,-1/3)