The general term of an A.P. whose first term is a and common difference is d, is given by:

1. T_n = 2a + (n − 1)d

2. T_n = $\dfrac{n}{2}[2a + (n − 1)d]$

3. T_n = a + (n − 1)d

4. T_n = $\dfrac{n}{2}[a + (n − 1)d]$

The nth term from the end of an A.P., whose first term, last term and common difference are a, l and d respectively, is given by:

1. l + (n + 1)d

2. l − (n − 1)d

3. l + (n − 1)d

4. l − (n + 1)d

Sum of n terms of an A.P. whose first term and last term are a and l respectively is given by:

1. S_n = $\dfrac{n}{2}(a + l)$

2. S_n = $\dfrac{n}{2}(a − l)$

3. S_n = $\dfrac{n}{2}(2a + l)$

4. S_n = $\dfrac{n}{2}[a + (n − 1)l]$

The sum of first n natural numbers is:

1. $\dfrac{n(n − 1)}{2}$

2. $\dfrac{n(n + 1)}{2}$

3. $\dfrac{n(n + 2)}{2}$

4. $\dfrac{n(n − 2)}{2}$