1樓:匿名使用者
(1)a4+64b4
=a4+64b4+16a2b2-16a2b2=(a2+8b2)2-(4ab)2
=(a2+8b2-4ab)(a2+8b2+4ab);
(2)x4+x2y2+y4;
=x4+2x2y2+y4-x2y2
=(x2+y2)2-(xy)2
=(x2+y2-xy)(x2+y2+xy);
(3)x2+(1+x)2+(x+x2)2
=1+2(x+x2)+(x+x2)2
=(1+x+x2)2;
(4)設b-c=x,a-b=y,則c-a=-(x+y),則(c-a)2-4(b-c)(a-b)
=[-(x+y)]2-4xy,
=(x-y)2,
所以(c-a)2-4(b-c)(a-b)
=(b-c-a+b)2
=(2b-a-c)2;
(5)x3-9x+8;
=x3-x-8x+8
=(x3-x)-(8x-8)
=x(x2-1)-8(x-1)
=x(x+1)(x-1)-8(x-1)
=(x-1)(x2+x-8);
(6)x3+2x2-5x-6
=x3+x2+x2+x-6x-6,
=(x3+x2)+(x2+x)-(6x+6)=x2(x+1)+x(x+1)-6(x+1)=(x+1)(x2-x-6)
=(x+1)(x+3)(x-2).
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