《整式的乘法课件PPT》.pptx 11页

'整式的乘法人教版数学八年级上册 问题:三家连锁店以相同的价格m(单位：元／瓶）销售某种商品，它们在一个月内的销售量（单位：瓶）分别是ａ，ｂ，ｃ．你能用不同的方法计算它们在这个月内销售这种商品的总收入吗？ 解法(一):先求三家连锁店的总销量,再求总收入,即总收入(单位:元)为:m(a+b+c)①解法(二):先分别求三家连锁店的收入,再求它们的和,即总收入(单位:元)为:ma+mb+mc②由于①和②表示同一个量,所以:m(a+b+c)=ma+mb+mc你能根据分配律得到这个等式吗? 乘法分配律:(a+b)c=ac+bc单项式与多项式相乘的方法:单项式与多项式相乘,就是用单项式去乘多项式的每一项,再把所得的积相加.由乘法公式可知:m(a+b+c)=ma+mb+mc 例5计算:(1)(-4)·(3+1),(2)(a-2ab)·ab解:(1)(-4)(3+1)=(-4)·(3)+(-4)·1=-12-4(2)(a-2ab)·ab=a·ab+(-2ab)·ab=- 单项式与多项式相乘的结果是一个多项式，其项数与因式中的项数相同 巩固练习：１.计算：(1)3a(5a-2b)(2)(x-3y)·(-6x)解(1)３a(5a-2b)=3a·5a+3a·(-2b)=15a-6ab(2)(x-3y)·(-6x)=x·(-6x)+(-3y)·(-6x)=-6x+18xy 单项式与多项式相乘时可先确定积的符号例：计算（１）２a·(3a-5b)(2)(-2b)(-4a+b)解（１）２a·(3a-5b)=2a·3a-2a·5b=6a-10ab(2)(-2b)(-4a+b)=2a·4a-2b·b=8a-2bshop.99114.com/50648237shop.99114.com/47869049shop.99114.com/48919163shop.99114.com/50666040shop.99114.com/48208512shop.99114.com/50644192shop.99114.com/50670170shop.99114.com/49738996shop.99114.com/50625722shop.99114.com/50675128shop.99114.com/50650100shop.99114.com/50608214shop.99114.com/50530312shop.99114.com/50823779shop.99114.com/47898747shop.99114.com/50508183shop.99114.com/50640413shop.99114.com/49771539shop.99114.com/49971819shop.99114.com/50659923shop.99114.com/50299198shop.99114.com/50646179shop.99114.com/50627572shop.99114.com/50674705shop.99114.com/50798018shop.99114.com/50662906shop.99114.com/50499147shop.99114.com/50657920shop.99114.com/50672964shop.99114.com/51126331shop.99114.com/51232986shop.99114.com/51129260shop.99114.com/51233446shop.99114.com/51131343shop.99114.com/51132188shop.99114.com/51126246shop.99114.com/49830982shop.99114.com/50855587shop.99114.com/51132012shop.99114.com/50532750shop.99114.com/50855990shop.99114.com/51023652shop.99114.com/51233435shop.99114.com/50866272shop.99114.com/51233066shop.99114.com/51004630shop.99114.com/51028921shop.99114.com/50798552shop.99114.com/51233029shop.99114.com/51235754shop.99114.com/50673234shop.99114.com/50673283shop.99114.com/50672593shop.99114.com/50847408shop.99114.com/50674016shop.99114.com/50857820shop.99114.com/50823805shop.99114.com/50802033shop.99114.com/51130583shop.99114.com/49610836shop.99114.com/51131153shop.99114.com/50668455shop.99114.com/50831388shop.99114.com/51239193shop.99114.com/50673281shop.99114.com/50673437shop.99114.com/50673209shop.99114.com/50669256shop.99114.com/51399270shop.99114.com/51396689shop.99114.com/51398726shop.99114.com/50521841shop.99114.com/50657958shop.99114.com/51405322shop.99114.com/41244405shop.99114.com/51407253shop.99114.com/51023949shop.99114.com/51408617shop.99114.com/51410378shop.99114.com/51410288shop.99114.com/51238418shop.99114.com/51407265shop.99114.com/48001267shop.99114.com/50637206shop.99114.com/51410820shop.99114.com/50498383shop.99114.com/51413017shop.99114.com/49312439shop.99114.com/51413260shop.99114.com/48900764shop.99114.com/51397406shop.99114.com/51410598shop.99114.com/51410528shop.99114.com/48211017shop.99114.com/41321718shop.99114.com/48795003shop.99114.com/51413553shop.99114.com/51399142shop.99114.com/51414416shop.99114.com/50673484 练习：1、化简x(x-1)+2x(x+1)-3x(2x-5)2、计算：　（１）(2--4)·(-9)(2)-xy(-x-y+1) 练习答案：1、解：x(x-1)+2x(x+1)-3x(2x-5)=x·x-x·1+2x·x+2x·1-3x·2x+3x·5=-x+2+2x-6＋15x＝－３＋16x2、解（１）－18+9+36(2)+- 小结：１、这节课你学到了哪些知识？２、你有什么想法要跟大家一起交流？'