初一上学期数学化简与合并同类项要求有过程2x²y³+(-4x²y³)-(-3x²y³)214a+47a+53a117x+138x-38x(x-1)-(2x+1)3(x-2)+2(1-2x)(8xy-3y²)-5xy-2(3xy-2x²)(a+b-c)+(b+c-a

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初一上学期数学化简与合并同类项要求有过程2x²y³+(-4x²y³)-(-3x²y³)214a+47a+53a117x+138x-38x(x-1)-(2x+1)3(x-2)+2(1-2x)(8xy-3y²)-5xy-2(3xy-2x²)(a+b-c)+(b+c-a
初一上学期数学化简与合并同类项要求有过程
2x²y³+(-4x²y³)-(-3x²y³)
214a+47a+53a
117x+138x-38x
(x-1)-(2x+1)
3(x-2)+2(1-2x)
(8xy-3y²)-5xy-2(3xy-2x²)
(a+b-c)+(b+c-a)+(c+a-b)
已知m=3x²-2xy+y² ,n=2x²+xy-3y²
其中x=1,y=3(先化简再求值)求m-n,m+n

初一上学期数学化简与合并同类项要求有过程2x²y³+(-4x²y³)-(-3x²y³)214a+47a+53a117x+138x-38x(x-1)-(2x+1)3(x-2)+2(1-2x)(8xy-3y²)-5xy-2(3xy-2x²)(a+b-c)+(b+c-a
2x·xy·y·y-4x·xy·y·y+3x·xy·y·y
=(2-4+3)x·xy·y·y
=x·xy·y·y(·乘号的省略形式)