The equation does not have and y variable in it: it is of the form x = c. Alternatively, the x coordinates of both points are the same and the y coordinates are not.
If you have an equation that looks like y=mx+b then the m is the slope. If you have two points then you use the formula Y2-Y1/X2-X1
By substitution
yes
length
To find the length of a side, you either measure it, or you calculate it. How you calculate it depends on what data is given. For example, if you have the coordinates of the endpoints of a line, you can calculate the length by using the Pythagorean theorem (or simply subtracting the coordinates of the two endpoints, if the line is perfectly vertical or perfectly horizontal).
If you have an equation that looks like y=mx+b then the m is the slope. If you have two points then you use the formula Y2-Y1/X2-X1
the parallel of latitude 23½ degrees south latitude marking the southern limit of Sun's vertical rays
guess it
By substitution
Not greatly. To graph an inequality, you start off graphing the corresponding equality. It is only then that you select one side or the other (with or without the graph itself), as the region of interest.
You cannot. As soon as you have a line segment you have a line.
To create shapes. Think about it, without vertical lines there would never be tv....
you cannot graph it without an equal sign and an x value.
Only basic calculators without graphing capabilities are allowed on the GRE exam.
yes
Example sentence - You can see each segment of the worm without a magnifying glass.
It depends on what you are graphing and the domain. If you are tracking daily temperature in your town, for example, the only difference will be in the y-intercept: that is how high or low your graph is. If you must show the origin on the chart, though, the vertical scale will be much greater. If graphing some aspect of thermodynamics, the Kelvin graph should be simpler because it is likely to go through the origin.