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因式分解:(1)x4+y4+z4-2x2y2-2y2z2-2x2z2(2)x7+x5+1(3)(x+y-2xy)(x+y

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因式分解:
(1)x4+y4+z4-2x2y2-2y2z2-2x2z2
(2)x7+x5+1
(3)(x+y-2xy)(x+y-2)+(xy-1)2
因式分解:(1)x4+y4+z4-2x2y2-2y2z2-2x2z2(2)x7+x5+1(3)(x+y-2xy)(x+y
(1)x4+y4+z4-2x2y2-2y2z2-2x2z2
=x4-2x2y2+y4-2y2z2-2z2x2+z4
=(x2-y22-2z2(x2+y2)+z4
=(x2-y22-2z2(x2-y2)+z4-4x2y2
=(x2-y2-z22-4x2y2
=(x2-y2-z2-2yz)(x2-y2-z2+2yz)
=[x2-(y+z)2][x2-(y-z)2]
=(x+y+z)(x-y-z)(x+y-z)(x-y+z);
(2)x7+x5+1
=x7+x6+x5-x6+1
=x5(x2+x+1)-(x3+1)(x3-1)
=(x2+x+1)[x5-(x-1)(x3+1)]
=(x2+x+1)(x5-x4+x3-x+1);
(3)设x+y=a,xy=b,
则(x+y-2xy)(x+y-2)+(xy-1)2
=(a-2b)(a-2)+(b-1)2
=a2-2ab-2a+4b+b2-2b+1
=a2-2ab-2a+b2+2b+1
=a2-2ab+b2-2a+2b+1
=(a-b)2-2(a-b)+1
=(a-b-1)2
=(x+y-xy-1)2
=[(x-1)(1-y)]2