# Modelling

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#1
I thought when ever e is to the power of a negative the graph should decrease why does this one increase then

Question 3c
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#2
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1 week ago
#3
It's not just e to a negative
Its minus e to a negative (so you flip what e to a negative would look like --> as e to a positive approaches infinity as x gets bigger then e to a negative decrease to approach 0, so when you do - e to a negative you flip e to a negative to see that it increases to approach zero).

Here
Attached is graph for - e^-x

Then we have the 300 term so we shift it up
The 100 scales it by 100,and the 0.5 makes it approach the steady value slower
Last edited by gyuigygh; 1 week ago
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#4
(Original post by gyuigygh)
It's not just e to a negative
Its minus e to a negative (so you flip what e to a negative would look like --> as e to a positive approaches infinity as x gets bigger then e to a negative decrease to approach 0, so when you do - e to a negative you flip e to a negative to see that it increases to approach zero).

Here
Attached is graph for - e^-x

Then we have the 300 term so we shift it up
The 100 scales it by 100,and the 0.5 makes it approach the steady value slower
So for this question 6c
Model 1 as t reaches infinity, e reaches 0
So 20000 x 0=0 therefore reaches 0 on curve
For model 2
19000 x 0 +1000 =1000
Is that why model 2 never reaches 0 because it's worth 1000?

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#5
(Original post by gyuigygh)
It's not just e to a negative
Its minus e to a negative (so you flip what e to a negative would look like --> as e to a positive approaches infinity as x gets bigger then e to a negative decrease to approach 0, so when you do - e to a negative you flip e to a negative to see that it increases to approach zero).

Here
Attached is graph for - e^-x

Then we have the 300 term so we shift it up
The 100 scales it by 100,and the 0.5 makes it approach the steady value slower
But for 1c
As t reaches infinity, e reaches 0
So why doesn't this curve reach 0
0
1 week ago
#6
(Original post by Jshek)
So for this question 6c
Model 1 as t reaches infinity, e reaches 0
So 20000 x 0=0 therefore reaches 0 on curve
For model 2
19000 x 0 +1000 =1000
Is that why model 2 never reaches 0 because it's worth 1000?

Yes. The exponential term goes to zero, but there is a + 1000, so that is what the price tends to.
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1 week ago
#7
(Original post by Jshek)
But for 1c
As t reaches infinity, e reaches 0
So why doesn't this curve reach 0
Badly drawn graph. It does tend to zero and after 60s, will be ~1℅ of the initial value. Check in
www.desmos.com
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#8
(Original post by mqb2766)
Badly drawn graph. It does tend to zero and after 60s, will be ~1℅ of the initial value. Check in
www.desmos.com
All the graph reaches 0 but never touches the x axis.... if my grapgh touches the x axis do I lose my mark then?
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1 week ago
#9
(Original post by Jshek)
All the graph reaches 0 but never touches the x axis.... if my grapgh touches the x axis do I lose my mark then?
Your graph should never actually touch x axis as its an asymptote. It can be close but it should never touch (coz that would infer if you went further in time then it would go below x axis and the y axis value would be negative, but that never happens).so leave a little gap that's at least big enough to clearly see
Last edited by gyuigygh; 1 week ago
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