111111

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111111

111111
111111

111111
有什么问题?先化简再求解?

(2)5a^2-[3a-2a+3+4a^2]=5a^2-4a^2-a-3=a^2-a-3=4+2-3=3
(3)15a^2b-5ab^2+4ab^2-12a^2b=3a^b-ab^=3(1/4)(-1/3)-(1/2)(1/9)=-(1/4)-(1/18)=-11/36
(4)4xy-[x^2+5xy-y^2-x^2-3xy+2y^2]=4xy-2xy-y^2=2xy-y^2=2(...

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(2)5a^2-[3a-2a+3+4a^2]=5a^2-4a^2-a-3=a^2-a-3=4+2-3=3
(3)15a^2b-5ab^2+4ab^2-12a^2b=3a^b-ab^=3(1/4)(-1/3)-(1/2)(1/9)=-(1/4)-(1/18)=-11/36
(4)4xy-[x^2+5xy-y^2-x^2-3xy+2y^2]=4xy-2xy-y^2=2xy-y^2=2(-1/4)(-1/2)-1/4=0
(5)3xyz+2x^2y+2y^2z-2xyz-xyz+2z^2x=2(x^2y+y^2z+z^2x)=2(-1+2+4)=10
(6)abc-[2ab-3abc+bc+4abc]=abc-abc-2ab-bc=-2*2(-1/2)-(-1/2)(-1)=2-1/2=3/2

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