8. Express the equation of the line passing through the points $(2,4)$ and $(2,-4)$ in general form.

Step 1 ：First, we find the slope of the line. Since the x-coordinates of both points are the same, the line is vertical and its slope is undefined.

Step 2 ：A vertical line has an equation of the form x = c, where c is a constant.

Step 3 ：Since the line passes through the point (2, 4), we can substitute x = 2 into the equation to find the value of c: x = 2.

Step 4 ：So the equation of the line in general form is x - 2 = 0.

Step 5 ：\(\boxed{x - 2 = 0}\)