2 marks A19. Which of the differential equations (1) / + zy' =VI (i1) ysinz=zy -z (m)y= =+! are linear? A: only (i) is linear B only (ii) is linear C: only (1) and (ii) are linear D: only (li) and (ifi) are linear E: only (ili) is linear 2 marks A20. Find the integrating factor (t) for the following linear differential equation ty' + 2y=t - 1+#. A: I = 2t B: I = e2t D. I = 24+1 EImet 2 marks A21. A general solution of the equation zy' ty = v= is A: VE + C B 3VI+ C: 3VE+C DVI+ E: 0 2 marks A22. Precisely one of the following lines IS NOT an axis of symmetry of the curve r = 3 cos(20). Which one? A: y = 0 B: 2=0 D: y= -I Ey = 2z