If \( f(1)=7 \) and \( f(n)=f(n-1)-4 \) then find the value of \( f(6) \).

Step 1 ：\( f(2) = f(1) - 4 = 7 - 4 = 3 \)

Step 2 ：\( f(3) = f(2) - 4 = 3 - 4 = -1 \)

Step 3 ：\( f(4) = f(3) - 4 = -1 - 4 = -5 \)

Step 4 ：\( f(5) = f(4) - 4 = -5 - 4 = -9 \)

Step 5 ：\( f(6) = f(5) - 4 = -9 - 4 = -13 \)