Answer:
Arithmetic sequence states that a sequence of numbers such that the difference between the consecutive terms is constant.
it is given by:
where a is the first term , n is the number of term and d is the common difference.
Given the series: 
here, Common difference(d) = 5
First term(a) = 49
by definition we have;
For nth term

= 5n + 44
To write the series using summation notation for 14 terms
Summation symbol 
The series for 14th terms is given by;

The highest common factor is 48.
Answer:
13
Step-by-step explanation:
because 3+9=12+1=13
Let

be any integer. Then

In other words:
(1) If

is a multiple of 4, then

.
(2) If dividing

by 4 leaves a remainder of 1, then

, since

for some integer

, and from (1) we know that

(because, obviously,

is a multiple of 4).
(3) If instead you get a remainder of 2, then

. This follows from (1) as well.

.
(4) Finally, if you get a remainder of 3, then

.