Find the sum of the first $25$ terms of the arithmetic sequence below.

$19, 28, 37,\dots$

Find the sum of the first $25$ terms of the arithmetic sequence below.

$1, 6, 11,\dots .$

What is the difference between the sum of the first $20$ terms and the next $20$ terms of the arithmetic sequence $6, 10, 14,\dots$?

Calculate the difference between the sums of the first $20$ terms of the arithmetic sequence $6, 10, 14,\dots$ and $15, 19, 23, ....$

The expressions for the sum to $n$ term of the arithmetic sequence is given below. Find the expression for the $n^{\mathrm{th}}$ term:

$n^2+2n$

The expressions for the sum to $n$ term of the arithmetic sequence is given below. Find the expression for the $n^{\mathrm{th}}$ term:

$2n^2+n$

The expressions for the sum to $n$ term of the arithmetic sequence is given below. Find the expression for the $n^{\mathrm{th}}$ term:

$n^2-2n$

The expressions for the sum to $n$ term of the arithmetic sequence is given below. Find the expression for the $n^{\mathrm{th}}$ term:

$2n^2-n$