I'm doing a review sheet right now and I really need the help please. The first term of an arithmetic sequence is 2, the fourth term is 11. Find the sum of the first 50 terms.

Question

anonymous · Answer

Listing down what we have:
$$a =2 $$
$$a_{4}= a + (n-1)d =11$$

Solving for d:
$$(2)+3d=11$$
$$3d=9$$
$$d=3$$

Sum of the first 50 terms:
$$\frac{ 50}{ 2 }(2a + 49d)$$
Since you are given "a" and have found "d", sub them in to solve the problem.