I don't understand function notation such as how to find fg(x) or how to use functions in a graph or table

Question

I don't understand how to find the domain or range in an equation and put it in a graph or what are the coordinates in the graph

Answer 1

Hi Ricardo;

Function is normally identified as f(x), not fg(x).  f(x)=y

But to go further in this matter...

Unfortunately. I cannot draw for you.  However, consider a graph to be a giant plus sign, +.  The line which goes from left-to-right is the x-axis.  It is the horizontal axis.  The line which goes up-and-down is the y-axis.  It is vertical.

 

x-axis---horizontal

y-axis---vertical

 

Do you have graph paper?  Graph paper is paper full of boxes, similar to this...

+++++++

+++++++

+++++++

+++++++

+++++++

 

Now consider the above to be a collection of boxes, with a giant + within it.

 

Let's say you need to find point 1,3.  This is x,y.  You will begin from the cross-hairs of the giant +.  On the x-axis, you will move one box to the right.  On the y-axis, you will move three boxes up.  That is point 1,3.

 

+++|#++

+++|*++

+++|*++

-----------

+++|+++

+++|+++

+++|+++

 

Let's say you need to find point -6,0.  You will begin from the cross-hairs of the giant +.  On the x-axis, you will move six boxes to the left.  On the y-axis, you will remain on the horizontal line and not move.  That is point -6,0.

 

++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++

#******------------

++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++

 

Let's say you need to find point 5,-2.  You will begin from the cross-hairs of the giant +.  On the x-axis, you will move five boxes to the right.  On the y-axis, you will move two boxes down.  That is point 5,-2.

 

++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++

-------------*****---

++++++|++++*+
++++++|++++#+
++++++|++++++
++++++|++++++
++++++|++++++
++++++|++++++

 

Of course, point 0,0 is the point of the cross-hairs of the giant +.

 

Does this help?  If not, please let me know.

Answer 2

Hi,

 

Well, unless you have a specific example to work with, I may not be able to guide you to understanding how to use functions in a graph or a table.  I think those are best understood with examples.

 

Domain is all the possible values that x can take on.  Range is all the possible values that y can take on.

 

f(g(x)) simply means evaluate g(x) first, then take that result and use it to evaluate f(x) where the "x" value in f(x) is whatever g(x) is.  Again, these situations, in my opinion, are best understood with examples.  If you have a specific problem related to these topics, feel free to post it.

 

Thanks.