已知x²-xy,xy-y²=-12,分别求式子x²-y²与x²-2xy+y²的值.
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![已知x²-xy,xy-y²=-12,分别求式子x²-y²与x²-2xy+y²的值.](/uploads/image/z/2733169-49-9.jpg?t=%E5%B7%B2%E7%9F%A5x%26%23178%3B-xy%2Cxy-y%26%23178%3B%3D%EF%BC%8D12%2C%E5%88%86%E5%88%AB%E6%B1%82%E5%BC%8F%E5%AD%90x%26%23178%3B-y%26%23178%3B%E4%B8%8Ex%26%23178%3B-2xy%2By%26%23178%3B%E7%9A%84%E5%80%BC.)
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.