Find the sum of `2n` terms of the series whose every even term is `' a '` times the term before it and every odd term is `' c '` times the term before it, the first term being unity.

The sum of 20 terms of a series of which every even term is 2 times the term before it, every odd term is 3 times the term before it, the first term being unity is a. (2/7)(6^(10)-1) b. (3/7)(6^(10)-1) c. (3/5)(6^(10)-1) d. none of these

Find the sum of n terms of the series whose n t h term is: 2n^2-3n+5

Find the sum of n terms of the series whose nth term is 12n^2-6n+5 .

Find the sum of n terms of the series whose nth term is: n(n^2+1)

Find the sum of n terms of the series whose nth term is: n(n-1)(n+1)

Find the sum of n terms of the series whose nth term is: n(n+3)

Find the sum of n terms of the series whose nth term is: n^3-3^n

Find the sum to n terms of the series whose nth term is 3n^(2)+2n

Find the sum to n terms of the series whose nth term is n^2+2^n .

Find the sum to n terms of the series whose nth term is n (n+2)