Question

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.

Answer 1

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.