Question 1060136
<pre><b>
You want the equation of this green vertical line:

{{{drawing(400,400,-10,10,-10,10, graph(400,400,-10,10,-10,10),
circle(8,3,.1), locate(8.1,3.4,"(8,3)"),
green(line(8,-11,8,11)) )}}}

Let's look at some other points on that green line:

{{{drawing(400,400,-10,10,-10,10, graph(400,400,-10,10,-10,10),
circle(8,3,.1), locate(8.1,3.4,"(8,3)"),
circle(8,5,.1), locate(8.1,5.4,"(8,5)"),
circle(8,-2,.1), locate(8.1,-2+.4,"(8,-2)"),
circle(8,-7,.1), locate(8.1,-7+.4,"(8,-7)"),
circle(8,-9,.1), locate(8.1,-9+.4,"(8,-9)"),
circle(8,8,.1), locate(8.1,8.4,"(8,8)"),




green(line(8,-11,8,11)) )}}}

What's true about all those points?

Their x-coodinate is always 8, never anything but 8.

So the equation is simply the statement

x = 8

That's all there is to it!  Just x = 8 because that
is true for every point on that vertical green line.

--------------------------------------------------

You want the equation of this green horizontal line:

{{{drawing(400,400,-10,10,-10,10, graph(400,400,-10,10,-10,10),
circle(8,3,.1), locate(8,3,"(8,3)"),
green(line(-11,3,11,3)) )}}}

Let's look at some other points on that green line:

{{{drawing(400,400,-10,10,-10,10, graph(400,400,-10,10,-10,10),
circle(8,3,.1), locate(8,3,"(8,3)"),
circle(-9,3,.1), locate(-9,3,"(-9,3)"),
circle(-6,3,.1), locate(-6,3,"(-6,3)"),
circle(-3,3,.1), locate(-3,3,"(-3,3)"),
circle(0,3,.1), locate(0,3,"(0,3)"),
circle(5,3,.1), locate(5,3,"(5,3)"),
circle(2,3,.1), locate(2,3,"(2,3)"),


green(line(-11,3,11,3)) )}}}

What's true about all those points?

Their y-coodinate is always 3, never anything but 3.

So the equation is simply the statement

y = 3

That's all there is to it!  Just y = 3 because that
is true for every point on that vertical green line.

--------------------------------------------------

You do the other one.  The equations of vertical and
horizontal lines have the simplest equations of all.
Vertical lines always have the equation "x = something".
Horizontal lines always have the equation "y = something".

Edwin</pre></b>