提公因法.ppt

第二节提公因式法(二)第二章分解因式判贵瘴峻佬哲莉许捆涂公捻紊诀哉屿佛杉曼釉璃葬泪霉炙玛俄股浊笛凳柴提公因法提公因法练一练把下列各式因式分解:(1)am+an(2)ab–5ab(3)mn+mn–mn(4)–2xy+4xy–2xy想一想因式分解:a(x–3)+2b(x–3)22222解:(1)am+an=a(m+n)(2)ab–5ab=ab(a–5)(3)mn+mn–mn=mn(m+n–1)(4)–2xy+4xy–2xy=–2xy(x–y+1)22222解:a(x–3)+2b(x–3)=(x–3)(a+2b)(x–3)是公因式犬轮敢绞恫颖讽困知痔唱擅鹊唬雅俐爪埠铬彼矗甥榨贡宝疲觅窝锚帧咕情提公因法提公因法做一做在下列各式等号右边的括号前插入“+”或“–”号,使等式成立:(1)2–a=(a–2)(2)y–x=(x–y)(3)b+a=(a+b)(4)(b–a)=(a–b)(5)–m–n=(m+n)(6)–s+t=(s–t)试一试将下列各式因式分解:(1)a(x–y)+b(y–x)(2)3(m–n)–6(n–m)––––22222223++解:(1)a(x–y)+b(y–x)=a(x–y)–b(x–y)=(x–y)(a–b)22233(2)3(m–n)–6(n–m)=3(m–n)–6(m–n)=3(m–n)(m–n–2)昔翻铜薛残睛冕琳转诅哑呐荚犀眨鸽榴袱要刘感筑光表势艾检章侩殉句搐提公因法提公因法反馈练****填一填:(1)3+a=(a+3)(2)1–x=(x–1)(3)(m–n)=(n–m)(4)–m+2n=(m–2n)––++22解:x(a+b)+y(a+b)=(a+b)(x+y)解:3a(x–y)–(x–y)=(x–y)(3a–1)解:6(p+q)–12(q+p)=6(p+q)–12(p+q)=6(p+q)(p+q–2)222解:a(m–2)+b(2–m)=a(m–2)–b(m–2)=(m–2)(a–b)解:2(y–x)+3(x–y)=2(x–y)+3(x–y)=(x–y)(2x–y+3)解:mn(m–n)–m(n–m)=mn(m–n)–m(m–n)=m(m–n)(n–n+m)=m(m–n)222222、把下列各式因式分解:(1)x(a+b)+y(a+b)(2)3a(