You have to subtract to the final result the initial one and divide it for the number of segments. Then, for every segment you add the number you found, for example:
Explanation: The formula is y-y1=m(x+b). Fill in what we know, which is, y-(-5)=-2/3 (x-3) Then you distribute and get y+5=-2/3x+2. Then you subtract 5 from each side and get your final answer of y=-2/3x -3
