Answer:
4
Explanation:
The difference between term n+1 and term n (for any n) is ...
f(n+1) - f(n) = (4(n+1) +6) - (4n +6)
= 4n + 10 - 4n -6
= 4
This is the common difference between any pair of adjacent terms.
_____
You can also recognize that this value is the value of the coefficient of n, so can you read the answer directly from the function definition.