Question

Of the 1 , a, n, d and Sn, determine the ones that are missing for each of the following arithmetic progressions

(i) a = -2, d= 5, Sn= 568
(ii) l = 8, n= 8, S8= -20
(iii) a= -3030, l= - 1530, n= 5
(iv) d= 2/3 , l= 10, n= 20​

Answer 1

Answer:

i)

Step-by-step explanation:

Answer 2

Answer:

i)a=−2,d=5,Sn=568

Sn=2n(2a+(n−1)d)=568

⇒2n(−4+(n−1)5)=568

⇒n(5n−9)=1136

⇒5n2−9n−1136=0

⇒n=2×59±81+4×5×1136

=109±151=16  −14.2

n=16

l=a+(n−1)d=−2+15×5+23

ii)l=8,n=8,S8=−20

l=a+(n−1)d⇒a+7d=8

S8=28(a+l)=