單項(xiàng)式與多項(xiàng)式相乘1.口算：(1)５x2y2.(-3x2y)(2)(x2)2.(-2x3y2)2(3)(1.2×103)·(5×102)原式=5×(-3)(x2x2)(y2y)原式=x4.4x6y4單項(xiàng)式乘以單項(xiàng)式的法則有幾點(diǎn)？①各單項(xiàng)式的系數(shù)相乘；②相同字母的冪按同底數(shù)的冪相乘;③單獨(dú)字母連同它的指數(shù)照抄.復(fù)習(xí)=4x10y4=-15x4y3原式=(1.2×5)×103×102=6×105

2.計(jì)算×24概括：單項(xiàng)式與多項(xiàng)式相乘，只要將單項(xiàng)式分別乘以多項(xiàng)式的每一項(xiàng)，再將所得積相加.單項(xiàng)式與多項(xiàng)式相乘公式：單項(xiàng)式與多項(xiàng)式相乘法則:過手訓(xùn)練：例1：計(jì)算：例2:計(jì)算：點(diǎn)評(píng)：(1)多項(xiàng)式每一項(xiàng)要包括前面的符號(hào)；(2)單項(xiàng)式必須與多項(xiàng)式中每一項(xiàng)相乘，結(jié)果的項(xiàng)數(shù)與原多項(xiàng)式項(xiàng)數(shù)一致；(3)單項(xiàng)式系數(shù)為負(fù)時(shí)，改變多項(xiàng)式每項(xiàng)的符號(hào).綜合訓(xùn)練變式：化簡求值：-2a2·(ab+b2)-5a(a2b-ab2)，其中a=1,b=-1.解:原式＝-2a3b-2a2b2-5a3b+5a2b2＝-2a3b-2a2b2-5a3b+5a2b2＝-7a3b+3a2b2

當(dāng)a=1,b=-1

時(shí)，原式＝-7×13×（-1）+3×12×（-1）2

=-7×1×（-1）+3×1×1=7+3=10課時(shí)小結(jié)：

1、單項(xiàng)式乘以多項(xiàng)式的乘法法則及注意事項(xiàng)；

2、轉(zhuǎn)化的數(shù)學(xué)思想.單項(xiàng)式與多項(xiàng)式相乘，就是用單項(xiàng)式去乘多項(xiàng)式的________,再把所得的積________每一項(xiàng)相加鞏固練習(xí)一.判斷××1.m(a+b+c+d)=ma+b+c+d()()3.(-2x)?（ax+b-3)=-2ax2-2bx-6x()×1.單項(xiàng)式與多項(xiàng)式相乘，就是用單項(xiàng)式去乘多項(xiàng)式的________,再把所得的積________二.填空2.4（a-b+1)=___________________每一項(xiàng)相加4a-4b+43.3x（2x-y2)=___________________6x2-3xy24.-3x（2x-5y+6z)=___________________-6x2+15xy-18xz5.(-2a2