因式分解 -X³+6X²+51X-280

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因式分解 -X³+6X²+51X-280
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因式分解 -X³+6X²+51X-280
因式分解 -X³+6X²+51X-280

因式分解 -X³+6X²+51X-280
-X³+6X²+51X-280
= -X³+5X²+X²-5X+56X-280
= -X²(X-5)+X(X-5)+56(X-5)
= -(X-5)(X²-X-56)
= -(X-5)(X-8)(X+7)

试根长除,一个根是5所以,有因子(x-5)长除得,(-x²+x+56)=-(x-8)(x+7)
所以,因式分解为-X³+6X²+51X-280 =-(x-5)(x-8)(x+7)或者写成(x-5)(8-x)(x+7)等

- X³ + 6X² + 51X - 280
=- X³ + 6X² + 42X + 9X - 343 + 63
=- (X³ +343) + (6X² + 42X) + (9X+ 63)
= -(X+7)(X² -7X+49) + 6X (X + 7) + 9 (X+ 7)
= (X+7...

全部展开

- X³ + 6X² + 51X - 280
=- X³ + 6X² + 42X + 9X - 343 + 63
=- (X³ +343) + (6X² + 42X) + (9X+ 63)
= -(X+7)(X² -7X+49) + 6X (X + 7) + 9 (X+ 7)
= (X+7) { -(X² -7X+49) + 6X + 9 }
= (X+7) { -X² +7X-49 + 6X + 9 }
= (X+7)(-X² +13X-40)
= -(X+7)(X² -13X+40)
= -(X+7)(X-5)(X-8)

收起

-X3+6X2+51X-280
=-(X3-6X2-51X+280)
= -(X3-5X2-X2+5X-56X+280)
= -[X2(X-5)-X(X-5)-56(X-5)]
= -(X-5)(X2-X-56)
= -(X-5)(X-8)(X+7)