The equation is y=-2x+4. The slope of a line is the change in the y axis divide by the change in the x axis. Therefore -2 is equal to change in y over change in x. Finding a point (x,y) and relating it to (4,-4) , the equation evolves to y-(-4) divide by x-4 equals -2. Further solving will give you y+4 = -2x+4. Simplification of this gives the solution.