Math Is Fun Forum

EddieRingle

Member

Registered: 2008-09-03

Posts: 2

Need a quick refresher

Just started 9th grade Geometry (I'm in an advanced class) and the teacher gave us a small assignment for the night. Summer was long and fun and now I need to "relearn" some bits of Algebra.

Basically, I am supposed to graph some data, I've made all three graphs like directed, but I am required to write a function for each graph that would contain the data points.

So, I really just need to be retaught how to write a function from the results of a graph.

Please respond ASAP.

Thanks!

mathceleb

Member

Registered: 2008-08-27

Posts: 19

Re: Need a quick refresher

Just started 9th grade Geometry (I'm in an advanced class) and the teacher gave us a small assignment for the night. Summer was long and fun and now I need to "relearn" some bits of Algebra.

Basically, I am supposed to graph some data, I've made all three graphs like directed, but I am required to write a function for each graph that would contain the data points.

So, I really just need to be retaught how to write a function from the results of a graph.

Please respond ASAP.

Thanks!

Are these straight line graphs?  If so, you would start by taking 2 of the points on the line, and forming the equation using the point-slope formula.  To see a coast to coast demonstration of this, go here:

Point Slope Line Equation

This shows you how to take 2 points, and form the slope of the line, the line equation, the distance between the 2 points, and the midpoint of the 2 points.

If your graphs involve more than straight lines, let me know.  if I don't have the lessons, I can search to find other resources for you.

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Math Celebrity

EddieRingle

Member

Registered: 2008-09-03

Posts: 2

Re: Need a quick refresher

The graph's slope.

mathceleb

Member

Registered: 2008-08-27

Posts: 19

Re: Need a quick refresher

The graph's slope.

Great, then you would just enter 2 points on the line in the calculator link I provided and it will show you exactly how to calculate slope.

Let me know if you have questions or want enhancements.

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Math Celebrity

EddieRingle

Member

Registered: 2008-09-03

Posts: 2

Re: Need a quick refresher

Hmm... are you sure we are on the same page? I meant the graph's have a curve to them, sorry.

mathceleb

Member

Registered: 2008-08-27

Posts: 19

Re: Need a quick refresher

Oh, I see, like a parabola?

Such as y = x^2?

I think the first step is to take your points and make an x/y chart.  I usually write down 3-4 points and then see how to write the function.

For example, you have points such as

x      y
0      1
1      2
2      5
3     10

You can see that you square x and add 1 to get to y.  So your function would be y = x^2 + 1.

Make sense?

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Math Celebrity

EddieRingle

Member

Registered: 2008-09-03

Posts: 2

Re: Need a quick refresher

Not a parabola, a curved line, like:

Chewy

Member

Registered: 2008-08-07

Posts: 67

Re: Need a quick refresher

Hi Eddie,

Hey, if you can give us some data to use, we may be able to give you some help. If they are three similar graphs, then data from one would be enough to help us see how to help you.