Answer:
believe it would be f(x)=-1/2x-1/2
Step-by-step explanation:
rise over run is y/x and looking at the graph as y decreases one x increases two giving us the slope(M) of -1/2 so using standard notation of y = mx+b we now have y=-1/2x+b now we need our b value we can find that by finding the y-int or where x=0 which again is -1/2 giving us the full equation of f(x)=-1/2x-1/2