Which of the following are partial differential equations? I. y\" + y = 0 II. xy\' + 4y = 0 III. d^2 y/dx^2 - 4y (dy/d pi) + x^2 y - d^3 y/dx^3 a) II, IV b) None of these. c) III d) I e) I, II, III, IV Solution All the equations are Ordinarey differential equations I . 2 nd order DE with constant coefficient . II . I order linear DE III . 3rd order DE . IV . I order DE ANS b. none of these.

1. Which of the following are partial differential equations? I. y" + y = 0 II. xy' + 4y = 0 III. d^2
y/dx^2 - 4y (dy/d pi) + x^2 y - d^3 y/dx^3 a) II, IV b) None of these. c) III d) I e) I, II, III, IV
Solution
All the equations are Ordinarey differential equations
I . 2 nd order DE with constant coefficient .
II . I order linear DE
III . 3rd order DE . IV . I order DE
ANS b. none of these