Given line have positive intercept but negative slope. So its equation can be written as

\dot{v} = -mx + v_c …..(i) [where \(m = \tan \theta = \frac{V_0}{K_0}\) ]

By differentiating with respect to time we get \(\frac{dv}{dt} - m \frac{dx}{dt} - n v\)

Now substituting the value of v from eq. (i) we get \(\frac{dv}{dt} = -m(-mx + v_x) - m^2 x - m v_x;\) \ \ a = m \ddot{x} - m \dot{v}_c

i.e. the graph between a and x should have positive slope but negative intercept on a -axis. So graph is correct.