First make a table of values of the function’s coordinates, and try to avoid coordinates that include decimals.
Second, find the first differences from the table you constructed. ( it should be 1)
There should be a 2 point gap in the x column if you chose the points (2,-4)(4,-3)(6,-2) (8,-2) and that is your denominator
Last, the y intercept (-5) is your b variable (y=mx +b)
The equation is
Y= x/2 -5
Sorry about my English