# Homework Help: Scatter plot, equation of exponential function

1. Feb 22, 2013

### pbonnie

1. The problem statement, all variables and given/known data
The copy of the question is in the image attached. I don't have a graphing calculator, and so am not sure how to determine the equation of the exponential function.

2. Relevant equations
y = a^x

3. The attempt at a solution
I made a scatter plot off of an online program (image also attached) but am unsure how to proceed. I could not find an online graphing calculator that could determine the equation.

#### Attached Files:

File size:
47.4 KB
Views:
171
• ###### questions2.png
File size:
11.8 KB
Views:
144
2. Feb 22, 2013

### rock.freak667

You can try to use microsoft excel to plot the graph and give you the equation of the trend.

If you need to show how to calculate the exponential function, you will need to lookup exponential regression lines.

3. Feb 22, 2013

### pbonnie

How would I find the equation that way?

4. Feb 22, 2013

### rock.freak667

http://mathworld.wolfram.com/LeastSquaresFittingExponential.html

this link should help.

However since the questions are meant to be done on a computer/calculator, just do a scatter plot in excel, right click on a point and add a trend line, then just change it to exponential.

5. Feb 23, 2013

### pbonnie

Okay great, thanks. I got the line of best fit - exponential, and it added an equation in the form y = A e^bx. But I'm not sure what that means. What is the "e" in the equation? and since the "bx" are both superscript, do you multiply them?

6. Feb 23, 2013

### rock.freak667

e is a mathematical constant like pi.

e ≈ 2.718281818...

the x is your independent variable. If A=2 and b=3, then your equation is y=2e3x.

7. Feb 23, 2013

### pbonnie

Oh okay. So if it came out with the equation y = 11246 e^0.291x, how would that be written to give the answer for the question b?

8. Feb 23, 2013

### rock.freak667

It would be written exactly like that, you would just need to define what 'y' represents and what 'x' represents.

9. Feb 23, 2013

### pbonnie

Oh. Okay thank you very much!