Question

已知x平方+y平方-4x-6y+13=0 ,求分式(y平方-x平方)分之x*y的值.

Answer 1

x^2+y^2-4x-6y+13=0

(x^2-4x+4)+(x^2-6y+9)=0

(x-2)^2+(y-3)^2=0

所以(x-2)^2=0,(y-3)^2=0

x-2=0,y-3=0

x=2,y=3

xy/(y^2-x^2)

=xy/(y+x)(y-x)

=2*3/5*1

=6/5