Puzzle of the Week #445 - Functional Equation

2*f(3/(3-x)) – f(x) = 135*x

 What is the value of f(4)?

 f(x) is a function of x. The above is a ‘functional equation’, where f() of more than one different value appears as an unknown. It may look intimidating, but if you approach it in the right way, it is solvable without any advanced mathematics. As a slight push in the right direction, see what happens if you let x=4.