已知x^2+y^2=7,xy=-2,5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)的值
问题描述:
已知x^2+y^2=7,xy=-2,5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)的值
答
5x^2-3xy-y^2-11xy+(-4x^2)-(-2y^2)
=x²+y²-14xy
=7+14×2
=35