Question

in an AP 1st term is 2,coomon difference is 8 .sum of nth term is 90.Find the number o terms and nth term​

Answer 1

Step-by-step explanation:

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Answer 2

Step-by-step explanation:

a= 2

D=8

Sn = 90

n/2 {2a+(n-1)D} =90

Putting values

n{4+8n-8} =180

8n^2 - 4n - 180= 0

2n^2 - n - 45 = 0

2n^2 - 10n + 9n - 45 =0

2n( n-5) +9( n-5) =0

(2n-9)(n-5)=0

2n-9 =0 or n-5=0

n=9/2 or n=5

9/2 is rejected

n=5

An = a+(n-1)D

= 2+(5-1)8

=2+32 = 34