Question

find the sum of first 25th terms of the ap whose first term and the common difference are 2 and -1 respectively ​

Answer 1

Answer:

- 250

Step-by-step explanation:

In APs, if first term is a and common differencr is d, sum of n terms is given by (n/2) [ 2a + ( n - 1 )d ]

Here,

a = first term = 2

d = common difference = - 1

So, sum of 25 terms is -

= > (25/2) [ 2(2) + ( 25 - 1 )(-1) ]

= > (25/2) [ 4 - 24 ]

= > (25/2) [ - 20 ]

= > ( - 25 * 20 / 2 )

= > - 250

Sum of first 25 terms is - 250