知识回顾v举例说明因式分解与整式乘法的关系v.我们已经学习了哪些因式分解的方法？v提公因式法: ma+mb+mc=m(a+b+c)v运用公式法: a2-b2=(a+b)(a-b) a2 2ab+b2=(a b)2(5)3ax2+6ax+3a(4) x5 - x3(1) x4 - y4(2) (y2 + x2 )2 - 4x2y2(6)2ax2+6ax+4a(3)x4-8x2+16.把下列各式因式分解：解:(1)x4-y4=(x2+y2)(x2-y2)=(x2+y2)(x+y)(x-y)(2)(y2+x2)2-4x2y2=(y2+x2+2xy)(y2+x2-2xy)=(x+y)2(x-y)2(3)x4-8x2+16=(x2-4)2=(x+2)2(x-2)2(4)x5-x3=x3(x2-1)=x3(x+1)(x-1)(5) 3ax2+6ax+3a=3a(x2+2x+1) =3a(x+1)2(6)2ax2+6ax+4a=2a(x2+3x+2)=2a(x+1)(x+2)1.(x+2)(x+1)=xx2 2+3x+2+3x+23 3.(x-2)(x+1)=.(x-2)(x+1)=xx2 2-x-
