Verified answer

The equation of a line having slope "m" and passing through the point (a,b) is

(y-b) = m(x-a)

This is called point-slope form of a line because, well, it's based on a point and a slope. When you are not given "m" directly you have to calculate it from other data.

* If you know another point (c,d) on the line, then m=(d-b)/(c-a). This is a common case

* If you know that the line is perpendicular to some other line of slope M, then m = -1/M

* If the line is expressed parametrically as a function of t: x=a+ut, y=b+vt, then m=v/u

So in general, find "m" from other data, and then plug into the point-slope form of the line.