Question 150728
Your variables will be x and y, since x and y are the variables in the coordinate plane.  The equation for a line is y=mx+b, so just plug in values for m and b, and you will have the equation of a line with two variables.  For the equation of a line with one variable, simply use x or y and assign a value.  For example:


y=mx+b
Plug in any old thing for m and b:
y=3x+5


Now plot it:
*[invoke describe_linear_equation -3, 1, 5]


Now take x or y (we will do both for examples):
y 
and assign a value
y=4


Now plot it:
*[invoke describe_linear_equation 0, 1, 4]


Now take x
x
and assign a value
x=2


Now plot it:
*[invoke describe_linear_equation 1, 0, 2]


That's all there is to it.