 June 06, 2020, 06:01:28 am

### AuthorTopic: Reciprocal functions help  (Read 235 times) Tweet Share

0 Members and 1 Guest are viewing this topic.

#### e2503

• • Posts: 12
• Respect: 0 ##### Reciprocal functions help
« on: September 15, 2019, 03:48:30 pm »
0
Hi everyone, I`m a bit confused about graphing reciprocal functions, if someone could send help it would be very much appreciated .
I was taught that when graphing reciprocal functions, i should first graph the original function in the denominator and work from then onwards. When graphing the original function do i have to graph the product of the denominator function and the numerator or just graph the denominator function? For instance, for y= -3x/ (x^2-16) do i graph -3x(x+4)(x-4) first or graph just (x+4)(x-4) as the original function?

#### RuiAce

• ATAR Notes Lecturer
• Honorary Moderator
• Great Wonder of ATAR Notes
•       • • Posts: 8738
• "All models are wrong, but some are useful."
• Respect: +2518 ##### Re: Reciprocal functions help
« Reply #1 on: September 15, 2019, 04:25:09 pm »
+1
I'm assuming this is for the new Year 11 syllabus?

If so, using the word "denominator function" is perhaps the cause of ambiguity here. The idea is that you should start with the sketch of $(x+4)(x-4)$, and then use that curve to sketch $\frac{1}{(x+4)(x-4)}$.

Then, you apply the multiplication technique on $-3x$ and $\frac{1}{(x+4)(x-4)}$.

(So in step 1, the original function is indeed $(x+4)(x-4)$. But in the second step, because we're doing a multiplication, there's technically speaking two "original" functions.)

Not sure how $-3x(x+4)(x-4)$ would be useful here, unless it's just a misinterpretation, or a typo.
« Last Edit: September 15, 2019, 04:28:46 pm by RuiAce »  