作业帮化简（或求值）(1).7xy-3x^2+2y^2-4xy +4x^2-3y^2(2).(5a^2-2ab)-2(3a2+
来源：学生作业帮 编辑：作业帮 分类：数学作业 时间：2024/07/16 17:49:32
化简（或求值）
(1).7xy-3x^2+2y^2-4xy +4x^2-3y^2
(2).(5a^2-2ab)-2(3a2+4ab-二分之一b^2)
(3).2x-(3x-二分之x-2)+[5x-二分之3(x-2)]
(4).8ab-4a^2b^2-8ab^2+2ab-2ab^2+4a^2b^2,（其中ab-ab^2=-2)
(1).7xy-3x^2+2y^2-4xy +4x^2-3y^2
(2).(5a^2-2ab)-2(3a2+4ab-二分之一b^2)
(3).2x-(3x-二分之x-2)+[5x-二分之3(x-2)]
(4).8ab-4a^2b^2-8ab^2+2ab-2ab^2+4a^2b^2,（其中ab-ab^2=-2)
(1).7xy-3x^2+2y^2-4xy +4x^2-3y^2
=7xy-4xy+4x^2 -3x^2+2y^2-3y^2
=3xy+x^2-y^2
(2).(5a^2-2ab)-2(3a2+4ab-二分之一b^2)
=5a^2-2ab-6a^2-8ab+b^2
=5a^2-6a^2-2ab-8ab+b^2
=-a^2-10ab+b^2
(3).2x-(3x-二分之x-2)+[5x-二分之3(x-2)]
=2x-3x+二分之x+2+[5x-二分之3x+1]
=-x+二分之x+2+5x-二分之3x+1
=5x-x+二分之x-二分之3x+2+1
=3x+3
(4).8ab-4a^2b^2-8ab^2+2ab-2ab^2+4a^2b^2,（其中ab-ab^2=-2)
8ab-4a^2b^2-8ab^2+2ab-2ab^2+4a^2b^2
=8ab+2ab+4a^2b^2-4a^2b^2-8ab^2-2ab^2
=10ab-10ab^2
=10(ab-ab^2)
=-2*10
=-20
=7xy-4xy+4x^2 -3x^2+2y^2-3y^2
=3xy+x^2-y^2
(2).(5a^2-2ab)-2(3a2+4ab-二分之一b^2)
=5a^2-2ab-6a^2-8ab+b^2
=5a^2-6a^2-2ab-8ab+b^2
=-a^2-10ab+b^2
(3).2x-(3x-二分之x-2)+[5x-二分之3(x-2)]
=2x-3x+二分之x+2+[5x-二分之3x+1]
=-x+二分之x+2+5x-二分之3x+1
=5x-x+二分之x-二分之3x+2+1
=3x+3
(4).8ab-4a^2b^2-8ab^2+2ab-2ab^2+4a^2b^2,（其中ab-ab^2=-2)
8ab-4a^2b^2-8ab^2+2ab-2ab^2+4a^2b^2
=8ab+2ab+4a^2b^2-4a^2b^2-8ab^2-2ab^2
=10ab-10ab^2
=10(ab-ab^2)
=-2*10
=-20
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