Question

If n term of an ap is given by sn =4n×n - 2n then the nth term of an ap is

Answer 1

Nth term = a+ ( n-1 ) d
( where a is the first term, n is the no. of terms
and d is the difference between two consecutive terms . )

seventh term = a7 = 1/9
ninth term = a9 =1/7
a7 = a + 6d - ( 1 )
a9= a+ 8d - ( 2 )
by subtracting ( 1 ) from ( 2 )
(+ )a+ 8d = 1/7 ( +)
( - )a+ 6d = 1/9 ( - )
= 2d = 2 /63
d = 1/63
by putting value of d in eq. ( 2 )
a + 8 ( 1/63 ) = 1/7
a + 8/63 = 1/7
a = 1/7 - 8/63
a = 1/63

a 63 = a + 62d
=1/63 + 62 ( 1 /63 )
= 1/63 + 62/63
= 1 ans.

Hope it helps you
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