Question

find the sum of first n terms of an AP whose first term is a and common difference is d​

Answer 1

Answer:

sum of first n terms in an A.P is( n/2 )[ 2a + (n-1) d ]

Answer 2

Answer:

$(n*a + \frac{(n-1)(n)(d)}{2})$

Step-by-step explanation:

1st term = a + 0d

2nd term = a + 1d

3rd term = a + 2d

...and so on

sum of 1st n terms = n*a + ((n - 1)n)d/2

= $(n*a + \frac{(n-1)(n)(d)}{2})$