The numbers
1/1, 1/2, ....., 1/2010
are written on a blackboard. A student chooses any two of the numbers, say
x, y, erases them, and then writes down xy+x+y.
He continues to do this until only one number is left on the blackboard. What is that number?
Find the function f(x), where:
f: R→R, and:
f(x+y)-f(x-y) = f(x)*f(y)
