(山东省滨州市无棣县埕口中学八年级数学上册 单项式与多项式相乘教学课件 华东师大版.ppt

巩固练习 * * * * * §14.2 整式的乘法 单项式与多项式相乘 2. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 1.单项式与单项式相乘法则： (1)各单项式的系数相乘; (2)相同字母的幂分别相乘; (3)只在一个单项式因式里含有的字母, 连同它的指数作为积的一个因式. (-ab2)(-3.5a3b5c2) =3.5 a4b7 c2 2. 什么叫多项式? 几个单项式的和叫做多项式。 在多项式中,每个单项式叫做多项式的项。 3. 什么叫多项式的项? 说出多项式2x2+3x-1的项和各项系数 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 算一算 m(a+b+c) =ma+mb+mc (m、a、b、c都是单项式) Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. m a b c (1)大长方形的长是________． (2)①、②、③三个小长方形的 面积分别是_____________． (3)由(1)、(2)得出等式 _______________________． ① ② ③ a+b+c ma、mb、mc m(a+b+c) 看图说明 ma mb mc =ma+mb+mc Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. (-2a)?(2a2-3a+1) =(-2a)?2a2 =-4a3+6a2-2a （乘法分配律） （单项式与单项式相乘法则） (-2a)?(-3a) (-2a)?1 + + Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 怎样叙述单项式与多项式相乘的法则? m(a+b+c)=ma+mb+mc (m、a、b、c都是单项式) Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 单项式与多项式相乘法则 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 m(a+b+c)=ma+mb+mc (m、a、b、c都是单项式) Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例1 计算： (1)(-4x)·(2x2+3x-1)； 解： (-4x)·(2x2+3x-1) ＝ ＝-8x3-12x2+4x 注意:(-1)这项不要漏乘，也不要当成是1； (-4x)·(2x2) (-4x)·3x (-4x)·(-1) + + Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 例1 计算： + Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. 单项式与多项式相乘时，分三个阶段： ①按乘法分配律把乘积写成单项式与单项式乘积的代数和的形式； ②单项式的乘法运算; ③再把所得的积相加. Evaluation only. Created with Aspose.Slides for .NET 3.5