2x-3y+1=0
t=2x
t-3y+1=0
y=(1+t)/3
x=t/2
x^2+y^2-6x+4y-12=0
(x-3)^2+(y+2)^2=25
x-3=X,y+2=Y
即向右平移3,向下平移2后:
X^2+Y^2=25