Solve the differential equation : $(x+y)dy + (x-y) dx=0$

Question

$\begin{array}{1 1}\text{a. $ tan^{-1} \frac {y}{x} + \frac {1}{2} log t | 1 + \frac {y}{x}| = log x + c$} \\ \text{b. $ tan^{-1} \frac {y}{x} + \frac {1}{2} log t | 1 + \frac {y^2}{x^2}| = log x + c$} \\ \text{c. $ tan^{-1} \frac {y}{x} + \frac {1}{2} log t | 1 + \frac {y^2}{x^2}| = - log x + c$} \\ \text{d. $ tan^{-1} \frac {y}{x} + \frac {1}{2} log t | 1 + \frac {y}{x}| = - log x + c$} \end{array} $