分解因式:(1)x3+3x2-4;(2)x4-11x2y2+y4;(3)x3+9x2+26x+24;(4)x4-12x+323
答案:1 悬赏:80
解决时间 2021-01-29 02:32
- 提问者网友:树红树绿
- 2021-01-28 11:35
分解因式:(1)x3+3x2-4;(2)x4-11x2y2+y4;(3)x3+9x2+26x+24;(4)x4-12x+323
最佳答案
- 二级知识专家网友:过活
- 2021-01-28 13:09
(1)x3+3x2-4
=x3+2x2+x2-4
=x2(x+2)+(x+2)(x-2)
=(x+2)(x2+x-2)
=(x+2)(x+2)(x-1)
=(x+2)2(x-1).
(2)x4-11x2y2+y4
=(x4-2x2y2+y4)-9x2y2
=(x2-y2)2-(3xy)2
=(x2-y2+3xy)(x2-y2-3xy).
(3)x3+9x2+26x+24
=(x3+2x2)+(7x2+14x)+(12x+24)
=x2(x+2)+7x(x+2)+12(x+2)
=(x+2)(x2+7x+12)
=(x+2)(x+3)(x+4).
(4)设x4-12x+323=(x2+ax+17)(x2+bx+19),
∴由多项式的乘法得到:x4+(a+b)x3+(36+ab)x2+(19a+17b)x+323=x4-12x+323.
∴a+b=0,
ab+36=0
19a+17b=-12.
∴a=-6,b=6.
∴x4-12x+323
=(x2-6x+17)(x2+6x+19).
=x3+2x2+x2-4
=x2(x+2)+(x+2)(x-2)
=(x+2)(x2+x-2)
=(x+2)(x+2)(x-1)
=(x+2)2(x-1).
(2)x4-11x2y2+y4
=(x4-2x2y2+y4)-9x2y2
=(x2-y2)2-(3xy)2
=(x2-y2+3xy)(x2-y2-3xy).
(3)x3+9x2+26x+24
=(x3+2x2)+(7x2+14x)+(12x+24)
=x2(x+2)+7x(x+2)+12(x+2)
=(x+2)(x2+7x+12)
=(x+2)(x+3)(x+4).
(4)设x4-12x+323=(x2+ax+17)(x2+bx+19),
∴由多项式的乘法得到:x4+(a+b)x3+(36+ab)x2+(19a+17b)x+323=x4-12x+323.
∴a+b=0,
ab+36=0
19a+17b=-12.
∴a=-6,b=6.
∴x4-12x+323
=(x2-6x+17)(x2+6x+19).
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