化简:(1)2a﹣3b+4a﹣5b(2)(3x2﹣xy﹣2y2)﹣(x2+xy﹣2y2)(3)5x2﹣[6x﹣2(x2﹣3x)+7x2]-七年级数学

题目简介

化简:(1)2a﹣3b+4a﹣5b(2)(3x2﹣xy﹣2y2)﹣(x2+xy﹣2y2)(3)5x2﹣[6x﹣2(x2﹣3x)+7x2]-七年级数学

题目详情

化简:
(1)2a﹣3b+4a﹣5b
(2)(3x2﹣xy﹣2y2)﹣(x2+xy﹣2y2
(3)5x2﹣[6x﹣2(x2﹣3x)+7x2]
题型:计算题难度:中档来源:福建省期中题

答案

解:(1)原式=2a+4a﹣3b﹣5b
=6a﹣8b;
(2)原式=3x2﹣xy﹣2y2﹣x2﹣xy+2y2
=3x2﹣x2﹣2y2+2y2﹣xy﹣xy
=2x2﹣2xy;
(3)原式=5x2﹣[6x﹣2x2+6x+7x2]
=5x2﹣6x+2x2﹣6x﹣7x2
=5x2+2x2﹣7x2﹣6x﹣6x
=﹣12x;

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