Question 476154
Think of the equation as a long series of points
that make up a straight line. The straight line and the 
equation are the same thing.
The convention for showing a point is:
(x,y)
You need both an x and a y to be a point, but they
must be points on this line.
You can determine the points this way:
(0,?)
(1,?)
(2,?)
(3,?)
(4,?)
(5,?)
etc.
Or, this way:
(?,0)
(?,1)
(?,2)
(?,3)
(?,4)
(?,5)
etc.
So, given the x or y, you can find the point that
falls on the line.
---------------
{{{ y = (1/2)*x + 5 }}}
The y-intercept occurs where {{{ x = 0 }}}
{{{ y = (1/2)*0 + 5 }}}
{{{ y = 5 }}} is the y-intercept
The graph is:
{{{ graph( 400, 400, -10, 10, -10, 10, (1/2)*x + 5) }}}
----------------------------
{{{ x = 2 }}}
This just says: No matter what number I choose for y, I will
alway have {{{ x = 2 }}}. The points on this line will look like:
(2,y), and y can be any number. This is plotted as a vertical line
--------------------------
{{{ y = (1/5)*x }}}
{{{ graph( 400, 400, -10, 10, -10, 10, (1/5)*x ) }}}