Problem of the Fortnight: A function
Let f(x, y) be a function, defined on the positive integers, having the following properties, which hold for all positive integers x and y:
f(x, x) = x;
f(x, y) = f(y, x);
(x + y)f(x, y) = yf(x, x + y).
What is f(18, 69)?
Winner
The winning solution to this problem was presented by Rob Brase.
Other correct solutions were by Wesley J. Botham, Christopher Haccius, Travis Johnston, Tyler Lemburg, and Huong Nguyen.
