已知x²+xy﹦2,xy-y²﹦-7,求下列代数式的值 x²+y² x²+3xy-2y²x²+y²和 x²+3xy-2y²的值
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![已知x²+xy﹦2,xy-y²﹦-7,求下列代数式的值 x²+y² x²+3xy-2y²x²+y²和 x²+3xy-2y²的值](/uploads/image/z/2516407-7-7.jpg?t=%E5%B7%B2%E7%9F%A5x%26%23178%3B%2Bxy%EF%B9%A62%2Cxy-y%26%23178%3B%EF%B9%A6-7%2C%E6%B1%82%E4%B8%8B%E5%88%97%E4%BB%A3%E6%95%B0%E5%BC%8F%E7%9A%84%E5%80%BC+x%26%23178%3B%2By%26%23178%3B+x%26%23178%3B%2B3xy-2y%26%23178%3Bx%26%23178%3B%2By%26%23178%3B%E5%92%8C+x%26%23178%3B%2B3xy-2y%26%23178%3B%E7%9A%84%E5%80%BC)
已知x²+xy﹦2,xy-y²﹦-7,求下列代数式的值 x²+y² x²+3xy-2y²x²+y²和 x²+3xy-2y²的值
已知x²+xy﹦2,xy-y²﹦-7,求下列代数式的值 x²+y² x²+3xy-2y²
x²+y²和 x²+3xy-2y²的值
已知x²+xy﹦2,xy-y²﹦-7,求下列代数式的值 x²+y² x²+3xy-2y²x²+y²和 x²+3xy-2y²的值
x²+xy-(xy-y²)=x²+xy-xy+y²=x²+y²=2-(-7)=9
x²+y²=9
x²+xy+2(xy-y²)=x²+xy+2xy-2y²=x²+3xy-2y²=2+2x(-7)=-12
x²+3xy-2y²=-12