As we can see, the graph goes up, then stays flat for a while, and then goes up again. The only equation where this is true is the second one, where first the line goes up with the equation f(x)=4x, and then it stays still with the equation f(x) = 5, which will be a straight line, since there is no x value, and then it goes up again with f(x)=2x-1
