text: For the equation of a line?\n\nSlope is change in y divided by change in x, so subtract y coordinates and x coordinates of the given points (x1,y1) and (x2,y2): (y1-y2)/(x1-x2).  \n\nSlope on a line is constant, so if (x,y) is ANY point on the line, then the slope between it and a known point is the same as the slope between 2 known points, so\n\n(y-y1)/(x-x1) = (y1-y2)/(x1-x2)\n\nFinally, move the x term over to the right side:\n\n(y-y1) = (y1-y2)/(x1-x2) * (x-x1)