因式分解(6) 送分

2009-01-16 11:19 pm
1. (x-y)^2+3(y-x)^3
2. (x-y)^2+2(y-x)
3. (x-y)^2-3(y-z)^3
4. x(2y-x)^2+2x^2(x-2y)
5. 2(x-y)-(y-z)^2
6. x^3+x^2+x+1
7. x^3-x^2-x-1

請列明計算步驟

回答 (1)

2009-01-17 12:10 am
✔ 最佳答案
1.
(x - y)2 + 3(y-x)3
= (x - y)2 - 3(x - y)3
= (x - y)2[1 - 3(x - y)]
= (x - y)2(1 - 3x + 3y)

2.
(x - y)2 + 2(y - x)
= (x - y)2 - 2(x - y)
= (x - y)[(x - y) - 2]
= (x - y)(x - y - 2)

3.
(x - y)2 - 3(y - z)3
只可展開,不可因式分解。

若果把 z 變成 x。
(x - y)2 - 3(y - x)3
= (x - y)2 + 3(x - y)3
= (x - y)2[1 + 3(x - y)]
= (x - y)2)(1 + 3x - 3y)

5.
2(x - y) - (y - z)2
只可展開,不可因式分解。

若果把 z 變成 x。
2(x - y) - (y - x)2
= 2(x - y) - (x - y)2
= (x - y)[2 - (x - y)]
= (x - y)(2 - x + y)

6.
x3 + x2 + x + 1
= (x3 + x2) + (x + 1)
= x2(x + 1) + (x + 1)
= (x2 + 1)(x + 1)

7.
x3 - x2 - x -1
沒有因式,不可進行因式分解。
(但三個負數之中,其一變成正號,則可以進行因式分解。)
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