Question

已知X方+6X+Y方-8Y+25=0求(X+Y)方-(X-Y)方的值

Answer 1

X^2+6X+9+Y^2-8Y+16=0

所以（X+3）^2+(Y-4)^2=0

所以X=-3,Y=4

所以(X+Y)^2-(X-Y)^2=4XY=4*4*(-3)=-48