Q18 of 110 Page 65

If the n^thterm of an A.P. is t_n = 3-5n, then the sum of the first n terms is

Given t_n = 3-5_n, t₁ = 3-5 = -2

Sum of n terms of an AP = S_n = a + t_n)

S_n = -2 + 3-5n) = 1-5n)

So the correct answer is B.

In a G.P, t₂ = and t₃ = . Then the common ratio is

If x 0, then 1 + sec x + sec²x + sec³x + sec⁴x + sec⁵x is equal to

The common ratio of the G.P. a^m-n, a^m, a^{m + n}is

If 1 + 2 + 3 + . . . + n = k then 1³ + 2³ + … + n³is equal to

Questions · 110

2. Sequences and series of real numbers

1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 1 1 1 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1 2 3 4 5 6 7 8 9 10 11 12 1 1 1 1 1 1 2 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

If the nthterm of an A.P. is tn = 3-5n, then the sum of the first n terms is