Question

1. Find the sum of indicated number of terms of
each of the following A.P.'s:
(i) 5, 2,-1,-4, -7, .......; n terms
1 3
(ii) -1,-
4' 2
(iii) 2, 4, 6, ......, 100 terms
......., 81 terms​

Answer 1

Answer:

I) N/2[13-3n]

ii) -15

III) 10100

Step-by-step explanation:

IT is right answer and if u like it please give me BRAINLIEST

Answer 2

Answer:

Step-by-step explanation:

1. Given,

a=18

d=  2

31 −18=−  2 5

​  Formula,

an  =a+(n−1)d  =18+(n−1)(−  2 5 )

an =  2 41−5n

​Sn =  2 n [2a+(n−1)d]

    =  2 n [2(18)+(n−1)(−  2 5  )]

=  2n [  2 41−5n  ]

Sn  =  4 41n−5n  

2

 

​