Hi.

Two questions.

1: f(m) = -2 / (-3+9m)

i got a domain (-infinity, 0.33) U (0.33, infinity) and range (-infinity, 0) U (0, inifinity). correct?

2: f(w) = 7 / ( -2 + |w| )

i have no idea about number two. help please~!

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- Mar 27th 2012, 11:12 PMtankertertDomain and range
Hi.

Two questions.

1: f(m) = -2 / (-3+9m)

i got a domain (-infinity, 0.33) U (0.33, infinity) and range (-infinity, 0) U (0, inifinity). correct?

2: f(w) = 7 / ( -2 + |w| )

i have no idea about number two. help please~! - Mar 27th 2012, 11:51 PMbiffboyRe: Domain and range
Domain can't include 2 or-2

- Mar 28th 2012, 12:04 AMtankertertRe: Domain and range
How did you get that?

- Mar 28th 2012, 12:09 AMprincepsRe: Domain and range
$\displaystyle |w| =\begin{cases}-w, & \text{if } w < 0 \\w, & \text{if } w \geq 0\end{cases}$

Hence :

$\displaystyle f(w) =\begin{cases}\frac{-7}{w+2}, & \text{if } w < 0 \\\frac{7}{w-2}, & \text{if } w \geq 0\end{cases}$

Hence , domain is :

$\displaystyle w \in (-\infty , + \infty) \backslash \{-2,2 \}$ - Mar 28th 2012, 10:14 PMtankertertRe: Domain and range
Really need help guys.

how do i find range for first question and second? - Mar 30th 2012, 05:25 PMHallsofIvyRe: Domain and range
Well, it would be far better to write "domain (-infinity, 1/3) U (1/3, infinity)". Do you see why?

Quote:

and range (-infinity, 0) U (0, inifinity). correct?

If we write $\displaystyle y= -2/(-3+ 9m)$ them $\displaystyle -3+ 9m= -2/y$ so $\displaystyle 9m= 3- 2/y$ and $\displaystyle m= 1/3 - 2/(9y)$. Now what value can y**not**be?

Quote:

2: f(w) = 7 / ( -2 + |w| )

**cannot**have -2+ |w|= 0 so we cannot have |w|= 2. What values of w are forbidden?

(This is the one biffboy was referring to.)

As for the range, again, let y= 7/(-2+ |w|) so that |w|- 2= 7/y so |w|= 2+ 7/y. What can y**not**be?

i have no idea about number two. help please~![/QUOTE]