若x2+y2-6y+4x+13=0,则x2-y2=_.
问题描述:
若x2+y2-6y+4x+13=0,则x2-y2=______.
答
∵x2+y2-6y+4x+13=0,即(x+2)2+(y-3)2=0,
∴x=-2,y=3,
∴x2-y2=4-9=-5.
故答案是:-5.