Question

23,21,19 ......(45 terms) sum of n number

Answer 1

Answer:

a = 23

d = -2

an = 45

an = a + ( n - 1 ) d

45 - 23 = ( n - 1 ) -2

22/-2 = n - 1

- 11+1 = n

-10 = n

Sum = n / 2 ( a + an )

= -10 / 2 ( 23 + 45 )

= -5 ( 68 )

= - 340