已知x²-xy=13,xy-y²=-5,分别求出式子x²-y²与x²-2xy+y²的值
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![已知x²-xy=13,xy-y²=-5,分别求出式子x²-y²与x²-2xy+y²的值](/uploads/image/z/3988919-47-9.jpg?t=%E5%B7%B2%E7%9F%A5x%26%23178%3B-xy%3D13%2Cxy-y%26%23178%3B%3D-5%2C%E5%88%86%E5%88%AB%E6%B1%82%E5%87%BA%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=13,xy-y²=-5,分别求出式子x²-y²与x²-2xy+y²的值
已知x²-xy=13,xy-y²=-5,分别求出式子x²-y²与x²-2xy+y²的值
已知x²-xy=13,xy-y²=-5,分别求出式子x²-y²与x²-2xy+y²的值
x²-xy=13 ①
xy-y²=-5 ②
①+②
得x²-y²=8
①-②
得x²-2xy+y²=18
x²-xy=13····a
xy-y²=-5·····b
a-b得:x²-2xy+y²=18
a+b得:x²+y²=8
已知x²-xy=13,xy-y²=-5,
x²-y²=x²-xy+(xy-y²)=13-5=8;
x²-2xy+y²=x²-xy-(xy-y²)=13-(-5)=18;