[" 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, prove that S_(12) = 3 (S_(8) -S_4)

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 A.P.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. prove that S_12=3(S_8-S_4) .

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. If S_(2n) = 5(S_n) , then prove (S_(6n))/(S_(3n))=17/8

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