Excel in math, science, and engineering
Suppose a function \(f : R → R\) satisfies the following conditions:
\((a) f(4xy) = 2y [f(x + y) + f(x -y)],\) for all \(x, y ∈ R\)
\((b) f(5) = 3\).
Find the value of \(f(2015)\).