Calculus

If $f(x, y)$ is a homogeneous function of degree $n$, then $x^2 f_{xx} + 2 x y f_{xy} + y^2 f_{yy}$ equals:

Options:

• (A) $n(n - 1) f$
• (B) $n^2 f$
• (C) $(n + 1) f$
• (D) $n(n + 1) f$