f(x) is a real valued function where f(xy) = [f(x)] + [f(y)] + f(x)f(y) for all real x,y. If f(2) = 1, then what is the value of f(12) ?
f(2) = f(2 × 1) = f(2) + f(1) + f(2).f(1) = 1
f(1) = 0
f(1)=f(2×12)=f(2)+f(12)+f(2).f(12)=0
2×f(12)=−1⇒f(12)=−12