單項(xiàng)式與多項(xiàng)式相乘課件 [初中數(shù)學(xué) 教學(xué)課件 課件]

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1、1.單項(xiàng)式乘法法則 單項(xiàng)式相乘，把它們的系數(shù)、相同字母分別相乘，對(duì)于只在一個(gè)單項(xiàng)式里含有的字母，則連同它的指數(shù)作為積的一個(gè)因式.:計(jì)算.)2()5.0(21)1(3222bcabcab7.4 7.4 單項(xiàng)式與多項(xiàng)式相乘單項(xiàng)式與多項(xiàng)式相乘cab2212241ba)8(63cb:解3222)2()5.0(21)1(bcabcab.773cba2.什么叫多項(xiàng)式?幾個(gè)單項(xiàng)式的代數(shù)和叫做多項(xiàng)式.,22x,x.1.3.乘法對(duì)加法的分配律acabcba)(:如.122xx:它的項(xiàng)是二二.講授新課講授新課.計(jì)算:就是用單項(xiàng)式去乘多項(xiàng)單項(xiàng)式與多項(xiàng)式相乘,即再把所有的積相加式的每一項(xiàng).,mcmbmacbam)()

2、,(都是單項(xiàng)式cbam)132(22aaa22)2(aa)3()2(aa1)2(a34a26a.2a:乘乘的的法法則則1 1.單單項(xiàng)項(xiàng)式式與與多多項(xiàng)項(xiàng)式式相相 注意注意:(1)單項(xiàng)式與多項(xiàng)式相乘單項(xiàng)式與多項(xiàng)式相乘,結(jié)果是一結(jié)果是一個(gè)多項(xiàng)式個(gè)多項(xiàng)式,其項(xiàng)數(shù)與因式中多項(xiàng)式的項(xiàng)其項(xiàng)數(shù)與因式中多項(xiàng)式的項(xiàng)數(shù)相同數(shù)相同.(2)計(jì)算時(shí)計(jì)算時(shí),要注意符號(hào)問(wèn)題要注意符號(hào)問(wèn)題,多項(xiàng)式中多項(xiàng)式中每一項(xiàng)都包括它前面的符號(hào)每一項(xiàng)都包括它前面的符號(hào),同時(shí)還要注同時(shí)還要注意單項(xiàng)式的符號(hào)意單項(xiàng)式的符號(hào).2.例題講解.:計(jì)算1例.);232(5.0)1(2ababab.3)(24)3(22bababbaab);()()2(22

3、22yxyxyyxyxx:解2ab)ab32(1)0.5ab(22 2a ab b)a ab b3 32 2a ab b(2 21 12 2)a ab b3 32 2(a ab b2 21 12 22 2a ab b)(a ab b2 21 13 32 2b ba a3 31 1;b ba a2 22 2baab224bab 3()32bab baab22423ab33ab238ba3212ba3xyx22xyyx22xy3y3xyx223)(24)3(22bababbaab)()()2(2222yxyxyyxyxx.1242ba;3y例2.如圖，計(jì)算左面圖形的體積（黃、紅長(zhǎng)方體的各項(xiàng)尺寸相等

4、）：3x3x2x2x2x+55 5)(2 2x x2 2x x2 2x x2 2)52()223()23(xxxxx316x240 x314x330 x)52(82xx)52(72xx藍(lán)紅黃解VVVV:藍(lán)紅VV 2235x.752x.課堂練習(xí)三:.1計(jì)算:.2化簡(jiǎn));3(3)1(22xyyxxy).1944()3)(4(22xxx);6)(3)(2(xyx);432(5)3(2 xxx);1(3)3()3()2(222xxxxxxx);21(363)3(2yxxyxyxy).14(2)(4(23332xxxxx);(5)21(2)1(2222abbaababa.小結(jié)四 1 1單項(xiàng)式與多項(xiàng)式相乘的依據(jù)是乘法單項(xiàng)式與多項(xiàng)式相乘的依據(jù)是乘法對(duì)加法的分配律對(duì)加法的分配律 2 2單項(xiàng)式與多項(xiàng)式相乘，其積仍是多單項(xiàng)式與多項(xiàng)式相乘，其積仍是多項(xiàng)式，項(xiàng)數(shù)與原多項(xiàng)式的項(xiàng)數(shù)相同，注項(xiàng)式，項(xiàng)數(shù)與原多項(xiàng)式的項(xiàng)數(shù)相同，注意不要漏乘項(xiàng)意不要漏乘項(xiàng) 3 3積的每一項(xiàng)的符號(hào)由原多項(xiàng)式各項(xiàng)積的每一項(xiàng)的符號(hào)由原多項(xiàng)式各項(xiàng)符號(hào)和單項(xiàng)式的符號(hào)來(lái)決定，注意運(yùn)用符號(hào)和單項(xiàng)式的符號(hào)來(lái)決定，注意運(yùn)用去括號(hào)法則去括號(hào)法則