Im not understanding this function stuff. 
Can someone please explain it to me. Here 
is an example problem. y^2=x+1 I know that 
you enter a number into one of the variables 
and solve for the other variable, but Im not 
sure what makes a problem like this functional 
or non functional.

   Just solve 

       y² = x+1

   for y.  

When you take square roots of both 
sides, you must include
   + and -.  So
             ___
       y = ±Öx+1

So for every value of x, (other than x = -1 
which gives only y = 0), there are two y-values.  
For example when x = 0, then y = ±1.  That is, 
we get two y-values, both 1 and -1, for only one 
x-value, 0.  This is what must never be
true of a function.  So therefore y² = x+1 
DOES NOT represent a function.  The
graph of y² = x+1 looks like this:

 
 
But the graph of a function must never pass over 
or under any part of itself.