If n is an integer, f(n) = f(n-1) - n and f(4)=15. What is the value of f(6)? Choose the correct choice:
A) 4  B) 0  C) 1  D) 2  E) 24

Rationale: since f ( n ) = f ( n - 1 ) - n then : f ( 6 ) = f ( 5 ) - 6 and f ( 5 ) = f ( 4 ) - 5 . as given that f ( 4 ) = 15 then f ( 5 ) = 15 - 5 = 10 - - > substitute the value of f ( 5 ) back into the first equation : f ( 6 ) = f ( 5 ) - 6 = 10 - 6 = 4 . answer : a . questions on funtions to practice :
Answer: A