Question

If the sum of first Sn=4n-n2. Find the common difference d

Answer 1

Answer:

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Step-by-step explanation:

D = 5

given

Sn =n ( 4n + 1 )

= 4n^2 + n

we know that,

an = Sn - S(n-1)

=4n^2+n -4 (n-1)^2 - (n-1)

=4 (n^2-n^2+2n-1)+(n-n+1)

=8n - 4 + 1

= 8n -3

hence ,

an = 8n -3

a1 =8 (1)-3 =5

a2= 8 (2)-3 =13

so, AP is 5, 13 , 21 and so on

• and D = 5