A) \[x+(n-1)a\]
B) \[x+(n+1)a\]
C) \[x+(n+2)a\]
D) \[x+an\]
Correct Answer: D
Solution :
(d): Sum \[=x+(x+a)+.........\] \[=(2n+1)x+[a+2a+3a+.......2n.a]\] \[=(2n+1)x+\frac{2n}{2}\{2a+(2n-1)a\}\] Or, \[{{S}_{n}}=(2n+1)x+\frac{2n}{2}\times a(2n+1)\] \[\therefore \] Mean \[=\frac{{{S}_{n}}}{2n+1}=x+na\]
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