 Ask Remember Me? cads2 Posts: 1, Reputation: 1 New Member #1 Nov 16, 2006, 08:18 PM
logarithmic function
I need to answer this logarithmic function. Label at least three points on the graph and vertical asymptote. y=3+log5x. kyop Posts: 48, Reputation: 11 Junior Member #2 Nov 16, 2006, 10:04 PM Originally Posted by cads2
I need to answer this logarithmic function. Label at least three points on the graph and vertical asymptote. y=3+log5x.
Since you are asking for specific points I will assume that you are just starting with graphing log functions. So, you probably could use a little refresher on how logs work. If not, sorry to give you too much information.

Logarithms are the undoing of exponents. 10^3 = 1000 would be written as
log (base 10) 1000 = 3.

Now, since this problem is working in base 10 (when it's not written you just assume base 10), you can actually capitalize on the 5x to make your problem especially easy.

For instance, what if you were to make x=2? That would create log (base 10) 5(2) or simply log(base 10) 10. This translates to 10^(?) = 10. The question mark is obviously a "1". So, log(base 10)10 = 1.

Substitute that in to your equation and you get: y = 3+1 or simply y = 4.

So, you used x=2 to generate y=4. Therefor (2,4) would be one of your points.

You can use x = 1/5 if you like. Yes, 1/5 isn't exactly a pretty x-value, but it will make y work out very well.

y = 3 + log 5(1/5)
y = 3 + log 1
y = 3 + 0 (since 10^0 = 1) - Let me know if you need instruction on this point
y = 3

So, (1/5, 3) is another point.

The only other point that would work well and still fit on a graph is x=20.
y = 3 + log 100
y = 3 + 2
y = 5

So, (20, 5) would be the third point.

As for the asymptote, can you ever find a value for x where 10^x = 0? The answer is no, you can't. So, your vertical asymptote would be the line x = 0.

I hope this helps. If you need any further explanation, let me know.

 Question Tools Search this Question Show Printable Version Email this Page Search this Question: Advanced Search

## Check out some similar questions!

Derivatives: Exponential and Logarithmic Functions [ 4 Answers ]

Is there any easy way to find the derivative of an exponential or logarithmic function? Or can anyone explain it simply?

TV Out Function On [ 0 Answers ]

I've got a DVD drive and the PowerDVD 5.0 player and every time I try to watch a newer DVD, I get the error message "TV out function error", I look at the details and it says I can't play copyright protected DVD's with the TVout function enabled. The weird thing is, ALL my graphics adapters just...

Exponential and Logarithmic functions [ 2 Answers ]

How do I find 1. Domain & Range 2. Intervals of increase/decrease 3. max./min values 4. intercepts 5. asymptotes 6. concavity for Exponential and Logarithmic functions. Can someone explain how I do this in detail plzzz

Trigonometric function [ 1 Answers ]

Please, I don't understand vector. I don't know how to solve or use it. :'( here are the question that I need help on. 1. Vector A points along the +y axis and has a magnitude of 100.00 units. Vector B points at an angle of 60.0 degrees above the + x axis and has a magnitude of 200.0 units....

Math function in vb [ 1 Answers ]

For 'Non intrinsic mathematical function" which library I have to insert/use ?