若x+y=6,xy=-8,求代数式(x+y-z)^2+(x+y-z)(x+y+z)-2·z(x-y)

(x+y-z)²+(x+y-z)(x+y+z)-2z(x-y)=[(x+y)-z]²+[(x+y)-z][(x+y)+z]-2z(x-y)=(x+y)²-2z(x+y)+z²+(x+y)²-z²-2z(x-y)=-2z[(x+y)+(x-y)]=-2z(2x)=-4xz 应该是式子错了!没有答案! 很高兴为您解答,祝你学习进步!【the 1900】团队为您答题。有不明白的可以追问!如果您认可我的回答。请点击下面的【选为满意回答】按钮。如果有其他问题请另发或点击向我求助,答题不易,请谅解,谢 再问： 对不起我打错了呢。。原式是若x+y=6,xy=-8,求代数式(x-y+z)^2+(x+y-z)(x+y+z)-2·z(x-y) 再答： (x-y+z)²+(x+y-z)(x+y+z)-2z(x-y) =[(x-y)-z]²+[(x+y)-z][(x+y)+z]-2z(x-y) =(x-y)²-2z(x-y)+z²+(x+y)²-z²-2z(x-y) =(x-y)²+(x+y)² =(x²-2xy+y²)+(x²+2xy+y²) =2x²+2y² =2(x²+y²) =2[(x+y)²-2xy] =2×[6²-2×(-8)] =2×(36+16) =2×52 =104