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The first and last elements of an A.P ar...

The first and last elements of an A.P are` a` and `l` respectively. If `S` is the sum of all terms of the A.P, then the common difference is

A

1)`(l^(2)-a^(2))/(2 S-(l+a))`

B

2)`(l^(2)-a^(2))/(2 S-(l-a))`

C

3)`(l^(2)+a^(2))/(2 S+(l+a))`

D

4)`(l^(2)+a^(2))/(2 S-(l+a))`

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A
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