The differential equation x -4 -3 y² dx + (y² + x−³ y² + 6) dy = 0 is = ☐ non exact and has integrating factor μ(y) y² e³y ☐ non exact and has integrating factor μ(x) = 2 x² e -2 ☐ non exact and has integrating factor μ(y) = y¯² e -3 x ☐ non exact and has integrating factor μ(y) = y³ e² y -3 y exact ☐ non exact and has integrating factor μ(x) -2 -3x = x e