First step, find the slope of the line, which is the change in y/change in x m= -4-0/4-0 = -4/4 = -1 m=-1 Now you can use one of the coordinates and the slope to set up a linear equation in point-slope form y-(-4)= -1(x-4) Distribute y+4= -1x+4 Get y by itself by subtracting 4 from each side y= -1x+0 Now the equation is in slope-intercept form, just one more step to get it into standard form. Move the x value to the side with y by adding 1x to each side. x+y=0