十万里加急!!! 高中数学题!!!!! 求助 大神, 希望有高人 耐心指点, thx 希望 我能早早的 被 贵人 找到!?

2017-08-06 10:29 pm
求解下题 并 提供 列式, 列式,因为这很重要, 能解说一下更好

Question No.1

Inquiry and Investigation

6.1 : Exploring the limitations of using the Factor Theorem to find the factors of a polynomial

Inquiry
Is the Factor Theorem always useful in factorizing the polynomial (尼度打唔度出来,只能。。) ax(3)+bx(2)+cx+d (即: a乘x的三次方 + b乘x的二次方 +c乘x + d ) into a product of linear factors?

Investigation Steps

1. Let (这里指函数) f(x) = x(3次方)+3x(2次方) -x-3.

(a) List all the possible linear factors of f(x).

(b) Using the Factor Theorem, determine whether each expression obtained in (a) is a factor of f(x).

(c) If we do not use long division, can f(x) be factorized into a product of linear factors? If yes, factorize f(x).

2. Let (这里指函数) g(x)= x(3次方) -2x(2次方) +7x-6.

(a) List all the possible linear factors of g(x).

(b)Using the Factor Theorem, determine whether each expression obtained in (a) is a factor of g(x).

(c) If we do not use long division, can g(x) be factorized into a product of linear factors? If yes, factorize g(x).

Conclusion

The Factor Theorem is (always / not always) useful in factorizing the polynomial ax(3)+bx(2)+cx+d (即: a乘x的三次方 + b乘x的二次方 +c乘x + d ) .

此题除求解外, 真心想知道 它背后想说什么,想教 我 什么。 (c) 部分,不用长除, f(x) 怎么被 factorized? ‘’怎么‘’? 它书中从未就此说过怎么。
还有, 我 忘了 什 么是 linear, linear factor 是怎样?(带x(1次方)?)另外还有什么玄机 诚望指出。

回答 (1)

2017-08-07 3:45 pm
一次因式檢驗法與有理根判別法(Linear factor test and determination of rational root)
Linear factor 就是線性因式, 簡言之就是一次因式

1. Let (这里指函数) f(x) = x(3次方)+3x(2次方) -x-3.

(a) List all the possible linear factors of f(x).
三次方係數 1 的因數有, 1, -1, 常數項係數 -3的因數有1, -1, 3, -3
(x+1), (x-1), (x+3), (x-3)
(b) Using the Factor Theorem, determine whether each expression obtained in (a) is a factor of f(x).
f(x) = x^3+3x^2 -x-3 = (x-1)(x^2+4x+3) ....Yes
f(x) = x^3+3x^2 -x-3 = (x+1)(x^2+2-3) ....Yes
f(x) = x^3+3x^2 -x-3 = (x-3)(x^2+1) 不合...No
f(x) = x^3+3x^2 -x-3 = (x+3)(x^2-1) ....Yes

(c) If we do not use long division, can f(x) be factorized into a product of linear factors? If yes, factorize f(x).
f(x) = x^3+3x^2 -x-3 = (x-1)(x^2+4x+3)=(x-1)(x+1)(x+3) ....Ans

這樣第二題就讓你自己練習了喔! You can practice the other by yourself.


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