1.35 Which of the following systems can be classified as linear/nonlinear, time-varying/time-invariant? (a) d²y(t) dr² +2ty(t) = f(1) (b) d²y(t) dy(t) dr² +y(t) + y(t)=4f(1) dt (c) dy(1) d³y(t) +2 dy(1) d14 dt3 - y(t)= dt dt df (t)-4f(1) (d) 125 di² 2 d²y(1) + y² (1) = f(1)