find equation of line which passes through the points (5,7) and (5,-8).

Is this undefined?

no. Just note that x=5 for both points. That means x=5 for all the points on the line. So, the line is

x=5

It is a vertical line.

To find the equation of a line passing through two points, you can use the formula for the slope-intercept form of a line, which is:

y = mx + b

where m is the slope of the line and b is the y-intercept.

To find the slope, you can use the formula:

m = (y2 - y1) / (x2 - x1)

Using the coordinates of the two points, (5, 7) and (5, -8), we can plug them into the formula to find the slope:

m = (-8 - 7) / (5 - 5)
m = -15 / 0

Since the denominator is 0, the slope is undefined. This means that the line is vertical and does not have a slope. However, we can still find the equation of the line based on its vertical nature.

The equation of a vertical line passing through a point (a, b) is:

x = a

In this case, since the line passes through the point (5, 7), the equation is:

x = 5

Therefore, the equation of the line passing through the points (5, 7) and (5, -8) is:

x = 5