2025年同步练习册配套检测卷六年级数学上册鲁教版五四制第61页答案
20. (8 分) 化简: $4(x + y + z) - 3(x - y - z) + 2(x - y - z) - 7(x + y + z) - (x - y - z)$.

答案

解：原式=[4(x+y+z)-7(x+y+z)]+[-3(x-y-z)+2(x-y-z)-(x-y-z)]
=-3(x+y+z)+(-2)(x-y-z)
=-3x-3y-3z-2x+2y+2z
=(-3x-2x)+(-3y+2y)+(-3z+2z)
=-5x-y-z