m2+n2=6n-4m-13
m2+n2-6n+4m+13=0
(m2+4m+4)+(n2-6n+9)=0
(m+2)2+(n-3)2=0
m+2=0,n-3=0
m=-2,n=3
m2-n2
=(-2)2-(3)2
=4-9
=-5
若m²+n²=6n-4m-13,则m²-n²=多少?
m2+n2=6n-4m-13
m2+n2-6n+4m+13=0
(m2+4m+4)+(n2-6n+9)=0
(m+2)2+(n-3)2=0
m+2=0,n-3=0
m=-2,n=3
m2-n2
=(-2)2-(3)2
=4-9
=-5