已知x^2+y^2=7,xy=-2,5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)的值
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![已知x^2+y^2=7,xy=-2,5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)的值](/uploads/image/z/1988655-15-5.jpg?t=%E5%B7%B2%E7%9F%A5x%5E2%2By%5E2%3D7%2Cxy%3D-2%2C5x%5E2-3xy-y%5E2-11xy%2B%28-4x%5E2%29-%28-2y%5E2%29%E7%9A%84%E5%80%BC)
已知x^2+y^2=7,xy=-2,5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)的值
已知x^2+y^2=7,xy=-2,5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)的值
已知x^2+y^2=7,xy=-2,5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)的值
5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)
=x²+y²-14xy
=7+14×2
=35
=x^2-14xy+y^2=7-14*(-2)=35
答案是35
展括号,合并同类项,后代入已知数据
5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)=(x^2+y^2)-14xy=7-(-28)=35