My Math Forum A 15 year old's math assignment has me stumped... any help?

 Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion

January 10th, 2018, 02:12 PM   #1
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From: The Netherlands

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A 15 year old's math assignment has me stumped... any help?

Hi All

my kid wants my help here, but I am stumped too.
The function(pl. see image) given has p & q as variables.

- the graph has the horizontal asymptote line y = -3
-the graph intersects at (-1,5)

find P and q.

Attached Images
 mth.jpg (84.7 KB, 13 views)

January 10th, 2018, 02:31 PM   #2
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$p$ and $q$ are unknown constants ... $x$ and $f(x)$ are the variables

$f(x) = \dfrac{p}{2x+1} - q$

Quote:
 - the graph has the horizontal asymptote line y = -3
$\displaystyle \lim_{x \to \infty} f(x) = -3 \implies q=3$ (why?)

Quote:
 - the graph intersects at (-1,5)
$5 = \dfrac{p}{2(-1)+1} - 3$

... solve for $p$

 January 10th, 2018, 02:59 PM #3 Member   Joined: Nov 2012 From: The Netherlands Posts: 33 Thanks: 2 You posed this to me: q=3 (why?) I wish I could tell you why ...but I am too out of touch here. I have passed it on to the kid and I hope he can find the why himself (after all, you have completely solved it all, & p =-8). * note: as I wrote, he showed me the why on his graph machine . the graph will otherwise be a +ve graph never touching 3. I think he got it ...and that's what counts. It was Fun! Thank You! Last edited by skipjack; January 10th, 2018 at 05:42 PM.
 January 10th, 2018, 05:46 PM #4 Global Moderator   Joined: Dec 2006 Posts: 18,416 Thanks: 1462 A graph machine? Thanks from Joppy
 January 11th, 2018, 03:29 AM #5 Member   Joined: Nov 2012 From: The Netherlands Posts: 33 Thanks: 2 I know..that sounded prehistoric it's his Casio Fx-9860GII Thanks from Joppy Last edited by hello_math; January 11th, 2018 at 03:33 AM.

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