已知x²-xy,xy-y²=－12,分别求式子x²-y²与x²-2xy+y²的值.

已知x²-xy,xy-y²=－12,分别求式子x²-y²与x²-2xy+y²的值.
已知x²-xy,xy-y²=－12,分别求式子x²-y²与x²-2xy+y²的值.

已知x²-xy,xy-y²=－12,分别求式子x²-y²与x²-2xy+y²的值.
假设x²-xy=a
相加
x²-xy+xy-y²=a-12
所以x²-y²=a-12
相减
x²-xy-xy+y²=a+12
所以x²-2xy+y²=a+12

x*x-y*y=(x*x-xy)+(xy-y*y)=-24;
x*x-2xy+y*y=(x*x-xy)-(xy-y*y)=0.