Consider the ordinary differential equation:
The partial differential equation \[ \frac{\partial^2 u}{\partial x^2} + 4 \frac{\partial^2 u}{\partial x \partial y} + 2 \frac{\partial^2 u}{\partial y^2} = 0 \] is ________.
Find the next two terms of the series:
The given series is: \( A, C, F, J, ? \).
(A) O
(B) U
(C) R
(D) V
Choose the correct answer from the options given below: