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已知A=2x3-xyz,B=y3-z2+xyz,C=-x3+2y2-xyz,且(x+1)2+|y-1|+|z|=0,求A-[2B-3(C-A)]的值.
人气:267 ℃ 时间:2019-08-20 03:13:36
解答
由(x+1)2+|y-1|+|z|=0,得
x+1=0
y−1=0
z=0

解得
x=−1
y=1
z=0

A-[2B-3(C-A)]=A-[2B-3C+3A]
=A-2B+3C-3A
=-2A-2B+3C
=-4x3+2xyz-2(y3-z2+xyz)+3(-x3+2y2-xyz)
=-7x3-2y3+2z2-3xyz,
x=−1
y=1
z=0
代入-7x3-2y3+2z2-3xyz=-7(-1)3-2×13+2×02-3×(-1)×1×0
=7-2+0-0
=5.
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