Top Posters
Since Sunday
5
a
5
k
5
c
5
B
5
l
5
C
4
s
4
a
4
t
4
i
4
r
4
Home Q & A Board Science-Related Homework Help Mathematics
New Topic  
Nuther Member Nuther Member
wrote...
Go to Answer
Posts: 13
Rep: 0 3
11 years ago
Well, i was out of school for a week and missed this lesson about determining if a graph was quadratic or exponential, and finding the equation for it. If the teacher gives you a few points on a graph, but it only shows half a parabola, or maybe all of the exponential, how can you determine the difference?

Also, how can you use this information and the points to find the equation for the graph.
Read 410 times
2 Replies
Replies
Answer accepted by topic starter
smooth15smooth15
wrote...
#1
Posts: 75
Rep: 0 0
11 years ago
Sign in or Sign up in seconds to unlock everything for free
This verified answer contains over 120 words.

Related Topics

wrote...
#2
11 years ago
If the points are consecutive, like (1,y1) (2,y2), (3,y3), etc, all you have to do to test if it's exponential is take y3/y2 then y2/y1 and see if the quotients are the same.  If yes, then it's exponential.  If not, you can test it as a quadratic by finding the second difference.  This means find the average rate of change between each pair of points, then take the average rate of change of the average rate of changes.  If those are constant then it's quadratic.

If the points are just random, like (1,y1), (5,y2), (12,y3), then you can test if it's exponential using ratios.  An exponential equation is y=Ca^x.  If you're given the vertical intercept, then this is very easy since you'll know C and will be able to substitute any of the coordinates to get the factor.  Then it's simple to check the other given points to see if they work in that equation.  If you don't have the vertical intercept, then you make a ratio of (y1=Ca^1)/(y2=Ca^5).  Then you divide and end up with y1/y2=a^-4 (C cancels and you use exponent rules to combine a^1/a^5).  Since you know what y1/y2 are (some constant), you raise both sides to the (-1/4) and you have a factor.  You'll have to use this to find the C, but then once you have an equation, you can use this to check your other points.
Julie Appleton
New Topic      
Quick Reply
Explore
Post your homework questions and get free online help from our incredible volunteers
  1251 People Browsing
Start New Topic Take the Tour CoursesNew Study Tools Topics Trending Browse by Textbook
Live Chat
Related Images
  
 186
  
 329
  
 256
Your Opinion
Which country would you like to visit for its food?
Votes: 204
Previous poll results: Should Ph.D.'s be addressed as doctors?