急!求-（x-y+z)-2(x-y+z)-3(x-y+z)的值,其中x=2,y= -1 z=3

题目

急!求-（x-y+z)-2(x-y+z)-3(x-y+z)的值,其中x=2,y= -1 z=3

答案

-（x-y+z)-2(x-y+z)-3(x-y+z)
=-x+y-z-2x+2y-2z-3x+3y-3z
=-6x+6y-6z
=-12-6-18
=-36
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