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

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