If `a = 1 , r = 2` find `Sn` for the `G.P`​

If in a G.P., a3 + a5 = 90 and if r = 2 find the first term of the G.P.

If Sn = 4n^(2) - n^(2) in an A.P. find the A.P.

If the functions f: R to R and g: R to R be defined by f (x) = 2x+1, g(x) = x^2 - 2. Find the formulae for g o f and f o g.

If P(5,r)=2,P(6,r-1), find r

If for a G.P., r=2 and t_(9) =128, then : a=

Sn1 and Sn2 reaction

Let f : R to R : f (x) = x^(2) + 2 "and " g : R to R : g (x) = (x)/(x-1) , x ne 1 . Find f o g and g o f and hence find (f o g) (2) and ( g o f) (-3)

If 7.5p_(r)=7p_(r-1) ,then find r

Let S_n denote the sum of first n terms of a G.P. whose first term and common ratio are a and r respectively. On the basis of above information answer the following question: The sum of product of first n terms of the G.P. taken two at a time in (A) (r+1)/r S_nS_(n-1) (B) r/(r+1)S_n^2 (C) r/(r+1)S_nS_(n-1) (D) none of these