A. maths

2008-06-08 5:03 am
Modulus Function :

Sketch graph f(x)= | x^2 - 4x +3 | for the domain 0<x<5 and state the corresponding range of f(x).
Can someone tell me how to find the corresponding range of f(x) ??
the answer is 0<f(x)<8 ... Why?

Thank you

回答 (2)

2008-06-08 5:24 am
First set x²-4x+3=0
(x-1)(x-3)=0
∴f(x)=0 when x=1 or 3, which is in the range of [0,5]
∴Min value of f(x)=0 as | x^2 - 4x +3 | must be greater than or =0
Consider tha shape of x²-4x+3, it is opening upward from the two sides, so it is obvious that the max. value occurs at the end pt.
f(0)=3
f(5)=8
∴Max. value of f(x)=8
∴range of f(x)=0 to 8
2008-06-08 5:20 am
i can tell you how to find the corresponding range of f(x)

consider
g(x)=x^2 - 4x +3
=(x-3)(x-1)

when x=1 or 3
g(x)=0

Since the cofficient of the x^2 is 1 , the graph is upward

This means that g(0) or g(5) should be the largest one

Since g(5)=8&gt;g(0)=3

And f(x)=|g(x)| should be &gt;=0

so the corresponding range of f(x) is

0&lt;=x&lt;8

2008-06-07 21:20:41 補充:
&gt >
&lt

2008-06-07 21:21:28 補充:
YAHOO時常想人手機認證

2008-06-07 21:46:28 補充:
because x=1 and x=3 is belonged to the domain 0<5

So the minmimum value of f(x) is 0

2008-06-07 21:48:00 補充:
AS YOU KNOW THAT


第一個人當然無表達得0甘好﹐因為無參考資料。


收錄日期: 2021-04-25 16:58:41
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080607000051KK02881

檢視 Wayback Machine 備份