Question

Ina an ap given a=2,d=8,sn=90​

Answer 1

Step-by-step explanati

Answer 2

Answer:

a=2,d=8,sn=90

sn=2n[2a+(n−1)d]90=2n[4+(n−1)8]

180=n[8n−4]

180=8n2−4n

=8n2−4n−180=0

=2n2−n−45=0

=2n2−10n+9n−45=0

=2n(n−5)−9(n−5)

=(2n−9)(n−5)

n=5

an=a+(n−1)dan=2+(5−1)8an=2+32an=34

Step-by-step explanation:

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