Question

Find Sum of n terms .
if a=6 ,d=8 aur n=19
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Answer 1

ANSWER

a=2,d=8,s n

=90s n

= 2n [2a+(n−1)d]90

= 2n [4+(n−1)8]180=n[8n−4]180=8n 2 −4n

=8n 2 −4n−180=0

=2n 2−n−45=0

=2n 2 −10n+9n−45=0

=2n(n−5)−9(n−5)

=(2n−9)(n−5)n=5a n

=a+(n−1)da n

=2+(5−1)8a n

=2+32a n =34