Questions on ln and e^x graphs

In summary, the conversation is about determining the domain, range, and line of asymptote for ln(x) and e^x graphs. There is confusion about the difference between the two graphs and how to find the domain and range. The conversation also touches on the use of the modulus function and the need for evaluating expressions to establish range and domain. Ultimately, it is suggested to manually plot the graphs and compare them to the given plot to determine the type of graph.
  • #1
Samurai44
57
0
Greetings,
I have some questions about ln(x) and e^x graphs , with figuring out Domain , range and line of asymptote.
Q1) How can I know if this graph is ln(x) or e^x

DSC_1066.JPG

(I thought it was e^x graph since there's no x-axis intercept , however the answer in marking scheme is:
Domain : xεR , x>-3
Range : yεR
Ast. : x=-3

So it is ln(x) since there is a x-range/value in the domain .(correct me if i am wrong)

Q2) what's the difference between the two following two graphs ,, and how can I find the domain and range ?

DSC_1068.JPG


DSC_1067.JPG


Its the Modulus function that confuses me and make it hard to get the domain value.

*No calculations are required from the above question, as it says "from the figure ... "

Thank you,
 
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  • #2
Those questions are weird. There is no way to derive the answers from the figures, other than some guessing.

For Q2 there are some formulas so you can work with that, but the graphs by themselves do not contain the information required, they only make sense as help in understanding the formulas.

Regarding the modulus, your formulas have the form ## \ln|X| ## where ## X ## is some expression - so you need to ask (a) what is the domain of the logarithm function, (b) what are the values of ## X ## such that its modulus falls in that domain, and (c) since ## X ## is an expression involving ## x ## , what are the corresponding values of ## x ## ?
 
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  • #3
For Q1 you can see the limits on ##x\to-\infty,\,x\to0,\,x\to+\infty## and compare with your graph.
 
  • #4
*No calculations are required from the above question, as it says "from the figure ... "
The fact that it says no calculations are required doesn't mean you shouldn't use your calculator to evaluate some expressions where this will help you to establish range or domain of the equations.

Q1) How can I know if this graph is ln(x) or e^x
The plot is neither of these, not exactly. But it does match the shape of one. I suggest that on a sheet of graph paper you manually plot the graphs y = ln(x) and y = e× and having done that compare with the plot you are given.
 
  • #5
theodoros.mihos said:
For Q1 you can see the limits on ##x\to-\infty,\,x\to0,\,x\to+\infty## and compare with your graph.

NascentOxygen said:
The fact that it says no calculations are required doesn't mean you shouldn't use your calculator to evaluate some expressions where this will help you to establish range or domain of the equations.The plot is neither of these, not exactly. But it does match the shape of one. I suggest that on a sheet of graph paper you manually plot the graphs y = ln(x) and y = e× and having done that compare with the plot you are given.

Thank you both
 

FAQ: Questions on ln and e^x graphs

1. What is an ln graph and how is it different from a regular graph?

An ln graph, also known as a natural logarithm graph, is a type of graph that plots the relationship between the natural logarithm of a number and its input value. The natural logarithm is the inverse of the exponential function, and as a result, the graph is a reflection of the graph of an exponential function over the line y=x.

2. How do you interpret the slope of an ln graph?

The slope of an ln graph represents the growth rate of the input values. A steeper slope indicates a faster growth rate, while a flatter slope indicates a slower growth rate. Additionally, the slope of an ln graph can also be used to calculate the percentage change between two points on the graph.

3. What is the significance of the horizontal asymptote on an ln graph?

The horizontal asymptote on an ln graph represents the value that the natural logarithm approaches as the input value approaches infinity. This value is known as the natural logarithm of infinity, which is equal to infinity itself. In other words, the graph will never touch or cross the horizontal asymptote, but it will get closer and closer to it as the input value increases.

4. How is an e^x graph related to an ln graph?

An e^x graph, also known as an exponential graph, is the inverse of an ln graph. This means that the x and y values on the two graphs are switched. For example, a point on the ln graph with coordinates (2, ln2) would have coordinates (ln2, 2) on the e^x graph. This relationship between the two graphs is crucial in solving exponential and logarithmic equations.

5. What are some real-world applications of ln and e^x graphs?

Ln and e^x graphs are used in various fields such as finance, biology, and physics. In finance, they are used to model compound interest and growth rates. In biology, they are used to model population growth and decay. In physics, they are used to describe the behavior of systems with exponential decay, such as radioactive decay. Additionally, they are also used in data analysis and trend forecasting.

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