1.
AD=AB+BC+CD=(X+4,Y-2)
BC=(X,Y)
向量BC//向量DA
(X+4)*Y=(Y-2)*X
XY+4Y=XY-2X
X=-2Y
2.
向量AC垂直于向量BD
BD=BC+CD=(X-2,Y-3)
AC=AB+BC=(X+6,Y+1)
(X-2)(X+6)=(Y-3)(Y+1)
X^2+4X-12=Y^2-2Y-3
4Y^2-8Y-12=Y^2-2Y-3
3Y^2-6Y-9=0
Y^2-2Y-3=0
Y1=3.Y2=-1
X1=-6,Y2=2