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Exponential or Inversely Proportional?

Quick question, how would you distinguish between these 2 types of graphs? Haven't got any examples; sorry for being so vague :colondollar:
Inversely proportional is a straight line with negative gradient. (See my correction edit below)
Exponential is curved either upwards or downwards depending on whether it's a positive or negative exponential.

The one below is a negative exponential for the temperature of an object that is cooling down.



Edit.
My apologies rushing the answers tonight. Inversely prop (eg y=1/x) is not a straight line. It looks very similar to the negative exponential.
(edited 11 years ago)
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Avatar for bmqib
bmqib
13
Original post by Stonebridge
Inversely proportional is a straight line with negative gradient.
Exponential is curved either upwards or downwards depending on whether it's a positive or negative exponential.

The one below is a negative exponential for the temperature of an object that is cooling down.



Doesn't inversely proportional imply y=1/x, so x can never be zero and vice versa? So we have a curve that looks like a negative exponential curve except it's not? Unless I am plotting y against 1/x maybe
Original post by bmqib
Doesn't inversely proportional imply y=1/x, so x can never be zero and vice versa? So we have a curve that looks like a negative exponential curve except it's not? Unless I am plotting y against 1/x maybe


Oops sorry. My mistake rushing the answers tonight. :redface:
Yes, inversely proportional is prop to 1/x and is not a straight line.
I was thinking for some reason of negative gradients.
And yes, the curve looks like a negative exponential like the one I posted.
With the difference being posted by the poster below.
(edited 11 years ago)
Erm... an exponential will go through (0,[1 or whatever e is multiplied by]), while 1/x is not defined at x = 0.
Original post by + polarity -
Erm... an exponential will go through (0,[1 or whatever e is multiplied by]), while 1/x is not defined at x = 0.


Yes.
Like this

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Avatar for aperk64
aperk64
1
While that is the case for an exponential relationship, what about an exponential decay relationship? how would someone be able to determine the difference between these two types of graphs
Wow. This thread was started 7 years ago and I have just returned to TSR after 5 years away. :smile:
If you are asking about the difference between an inverse square and an exponential decay, the simplest visual test, is to look at the value at x=0.
Normally an exponential delay curve starts at some definite point on the y axis and then falls gradually to zero along the x or (very often) the time axis.
An inverse square curve is undefined at x=0 because 1 divided zero is 'infinity'. So it would not have that defined starting point on that vertical y axis as the exponential decay curve would. In fact, it would not touch the y axis at all.

Let me know if this is helpful.

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