There is a problem with sample 1: -2x + 4 = 4 isn't a line!Originally Posted by Silly.girl
Generally what you want is the "perpendicular distance" between a point and a line. There is a general formula out there (I don't have it handy), but this is the basic logic of how to find it if you don't have the formula:
1. Solve the equation of the line (line 1) in slope-intercept form.
2. You want to find the equation of a line (line 2) passing through your point that is perpendicular to the original line (line 1). Thus the slope of line 2 will be -1/m(1).
3. Now you need to find the point of intersection of the two lines.
4. Now find the distance between the point of intersection and your point.
It's long and it's messy, but if you do it step by step it's really not that bad.