The point-slope equation formula is , where is the slope of the line and is a point on the line.
In our problem, we are adding $200 for each week , or we are changing each week by +200. This means that our slope , which is essentially the change of the line, is 200. The problem also gave us a coordinate point on the line, which was that at week 4, or when , we have $1700 in the account, or . Thus, the coordinate point is .
Using this information, we can find the equation of the line:
The answer is (y - 1700) = 200(x - 4).