Question

化简求值2x-y+3z)(-2x-y-3z)-(x+2y-3z)^2 其中X=1，y=-1，z=1

快啊，5分钟急要啊
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Answer 1

原式=[(2x+3z)-y][-(2x+3z)-y]-(x+2y-3z)^2
=-(2x+3z)^2+y^2-(x+2y-3z)^2
=-(2+3)^2+1-(1-2-3)^2
=-25+1-16
=-40

追问

a的3次方÷a·1/a???怎么算啊？？

追答

a的3次方÷a·1/a

=a^(3-1-1)
=a

追问

若5的m次方=4,5的n次方=2,求（1)5的（m+n)次方（2）5的（3m-2n）次方

追答

5的(m+n)次方=5^m*5^n=4*2=8

5^(3m-2n)=5^3m/5^2n=4^3/2^2=64/4=16

Answer 2

直接代入计算：
（1）（2x-y+3z)(-2x-y-3z)-(x+2y-3z)^2
＝-（2x-y+3z)(2x+y+3z)-(x+2y-3z)^2
=-（2+1+3)(2-1+3)-(1-2-3)^2
=-6x4-16
=-40

Answer 3

(2x-y+3z)(-2x-y-3z)-(x+2y-3z)^2=[-y+(2x+3z)][-y-(2x+3z)]-(x+2y-3z)^2
=y^2-(2x+3y)^2-(x+2y-3z)^2=-24-16=-40

Answer 4

-49