If `S_n` denotes the sum of first `n` terms of an A.P., prove that `S_(12)=3(S_8-S_4)` .

If S_n denotes the sum of first n terms of an AP, prove that S_(12) = 3 (S_(8) -S_4)

If S_(n) denotes the sum of first n terms of an AP, then prove that S_(12)=3(S_(8)-S_(4)).

If S_(n) denotes the sum of first n terms of an AP, then prove that S_(12)=3(S_(8)-S_(4)).

If S_n denotes the sum of the first n terms of an A.P., prove that S_(30)=3(S_(20)-S_(10)) .

If S_(n) denotes the sum of the first n terms of an A.P.prove that S_(30)=3(S_(20)-S_(10)).

If S_(n) denotes the sum of first n terms of an A.P., then (S_(3n)-S_(n-1))/(S_(2n)-S_(n-1)) is equal to

If S_(n) denotes the sum of n terms of a G.P., prove that: (S_(10)-S_(20))^(2)=S_(10)(S_(30)-S_(20))

If S_(n) denotes the sum of first n terms of an A.P. and S_(2n)= 3S_(n) , then (S_(3n))/(S_(n))=

If S_(n) , denotes the sum of first n terms of a A.P. then (S_(3n)-S_(n-1))/(S_(2n)-S_(2n-1)) is always equal to