The answer is y=-4x because you have to look at the graphs rise over run(or change in y over change in x). The graph is counting by 4s on the y axis and by 1 one the x axis. So the rise over run is 4 over 1 which gives you four. So it rises 4 units for every 1 unit it runs. Then to figure out if it is negative you look at the numbers on the x-axis and because they are negative the line has a negative slope.
