f(xy)=f(x+y) .f(7)=7. f(49)=.....

f(49) = f(7.7) = f(7 + 7) = f(14)
f(14) = f(7.2) = f(7 + 2) = f(9)
f(9) = f(3.3) = f(3 + 3) = f(6)
f(6) = f(6.1) = f(6 + 1) = f(7) = 7

Maka f(49) = 7.

Semoga membantu dan rajinlah belajar.