已知x+y=-1,xy=-2,求代数式-5（x+y)+(x-y)+x(xy+y)的值_数学解答

已知x+y=-1,xy=-2,求代数式-5（x+y)+(x-y)+x(xy+y)的值

人气：239 ℃　时间：2020-04-07 11:44:28

解答

答：
x+y=-1,xy=-2
-5（x+y)+(x-y)+x(xy+y)
=-5x-5y+x-y+xy(x+1)
=-4x-6y+(-2)(x+1)
=-4x-6y-2x-2
=-6x-6y-2
=-6(x+y)-2
=-6×(-1)-2
=6-2
=4