Recall that the constant of variation of a straight line is the slope of the line.
To compute the slope we will use the following formula for the slope of a line:
[tex]s=\frac{y_2-y_1}{x_2-x_1}\text{.}[/tex]
Now, notice that points (-1,3) and (1,-3) are on the line, then substituting these points in the above formula we get:
[tex]s=\frac{3-(-3)}{-1-1}=\frac{6}{-2}=-3.[/tex]
Answer: -3.
