作业帮合并下列各式的同类项①3m²n+5mn²+6nm²-4n²m-mn²②3(a+b)²-(a-b)+2(a+b)²+4(a-b)-(a+b)²
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合并下列各式的同类项①3m²n+5mn²+6nm²-4n²m-mn²②3(a+b)²-(a-b)+2(a+b)²+4(a-b)-(a+b)²
合并下列各式的同类项
①3m²n+5mn²+6nm²-4n²m-mn²
②3(a+b)²-(a-b)+2(a+b)²+4(a-b)-(a+b)²
合并下列各式的同类项①3m²n+5mn²+6nm²-4n²m-mn²②3(a+b)²-(a-b)+2(a+b)²+4(a-b)-(a+b)²
①3m²n+5mn²+6nm²-4n²m-mn²
=(3+6)m²n+(5-4-1)mn²
=9m²n
②3(a+b)²-(a-b)+2(a+b)²+4(a-b)-(a+b)²
=(3+2-1)(a+b)²+(4-1)(a-b)
=4(a+b)²+3(a-b)
3m²n+5mn²+6nm²-4n²m-mn²
=3m²n+6nm²+5mn²-4n²m-mn²
=9m²n
3(a+b)²-(a-b)+2(a+b)²+4(a-b)-(a+b)²
=3(a+b)²+2(a+b)²-(a+b)²-(a-b)+4(a-b)
=4(a+b)²+3(a-b)
合并下列各式的同类项
①3m²n+5mn²+6nm²-4n²m-mn²
=(3m^2n+6m^2n)+(5mn^2-4mn^2-mn^2)
=9m^2n
②3(a+b)²-(a-b)+2(a+b)²+4(a-b)-(a+b)²
=[3(a+b)^2+2(a+b)^2-(a+b)^2]+[-(a-b)+4(a-b)]
=4(a+b)^2+3(a-b)
1、把m（或n）都放前面，就看得出那些事同类项了
原式=3m²n+5mn²+6m²n-4mn²-mn²=3m²n+6m²n+5mn²-4mn²-mn²=9m²n
2、原式=3(a+b)²+2(a+b)²-(a+b)²-(a-b)+4(a-b)=4(a+b)²+3(a-b)
1.=(3m^2n+6m^2n)+(5mn^2-4mn^2-mn^2)
=9m^2n
2.=[3(a+b)^2+2(a+b)^2-(a+b)^2]+[-(a-b)+4(a-b)]
=4(a+b)^2+3(a-b)
1)9m²n
2)4(a+b)²+3(a-b)