Question

Find the formula for another line passing through(1,7) and (2,-2)

Answer 1

Use point slope formula
(y2-y1) / (x2-x1)

Answer 2

so its (-2 - 7) / (2-1) = -9 / 1 =
-9 is your answer for slope

Answer 3

The first part is not point slope formula

Answer 4

It's the formula to get the slope between two points

Answer 5

point slope is

y-y1=m(x-x1)

Answer 6

where (x1,y1) is one of your points while m is your slope.
@ilikephysics2 showed you how to get the slope and you are given two points in the question so use either one and you are set. PLug and enjoy your answer.