Question

find the A.P Given a=2,d=8,Sn=90 find n and an​

Answer 1

Answer:

a=2,d=8,s

n

=90

s

n

=

2

n

[2a+(n−1)d]

90=

2

n

[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=5

a

n

=a+(n−1)d

a

n

=2+(5−1)8

a

n

=2+32

a

n

=34

Step-by-step explanation:

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Answer 2

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n = 5

an = 34