SOLUTION: how do you graph y=3?

Question 1106906: how do you graph y=3?
Found 2 solutions by addingup, greenestamps:
Answer by addingup(3677) (Show Source): You can put this solution on YOUR website!
Graphs work on a grid system where you have lines going up and down and across. It's called a coordinate system.
To graph a point you need both the x and y coordinates. Why? Imagine a fly landed on your bedroom wall. You try to tell someone where exactly the fly landed, you'd have to tell them where across the wall and how high.
Here is a typical coordinate system:

Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!

The other tutor didn't answer your question. Or, rather, he interpreted your question in a way I don't think you intended -- thinking that you were plotting a single point instead of a line.

If you are plotting a single point, "y=3" is not enough information; you need an x value also.

But plotting the line "y=3" is something very different.

In the equation "y=3", we are told nothing about x. That means x can be any number we choose; the only restriction is that y must be 3.

So if you plot a whole bunch of points using different x values, keeping the y value always 3, what does the graph look like?

It is a horizontal line, crossing the y-axis at (0,3).

Most beginning students think of the x value of a point as how far the point is horizontally from the origin, and the y value as how far the point is vertically from the origin.

But in fact the x value tells you how far you are from the y-axis, and the y value tells you how far you are from the x-axis.

So "y=3" tells you that you are 3 units from the x-axis; since it doesn't tell you anything about the x value, you can choose any x value you want. The resulting graph is a horizontal line.

Similarly, the equation "x=4" would tell you that you are 4 units to the right of the y-axis, without telling you anything about the y value. So the graph of x=4 is a vertical line crossing the x-axis at (4,0).
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