If a, b and c are in arithmetic progression, then the roots of the equation ax - 2bx + c = 0 are

• $1 \mathrm{and} \frac{\mathrm{c}}{\mathrm{a}}$

• $- \frac{1}{\mathrm{a}} \mathrm{and} - \mathrm{c}$

• $- 1 \mathrm{and} - \frac{\mathrm{c}}{\mathrm{a}}$

• $- 2 \mathrm{and} - \frac{\mathrm{c}}{2\mathrm{a}}$

Let the coefficients of powers of x in the 2nd, 3rd and 4th terms in the expansion of (1 + x)ⁿ, where n is a positive integer, be in arithmetic progression. Then, the sum of the coefficients of odd powers of x in the expansion is

• 32

• 64

• 128

• 256

The sum 1 x 1! + 2 x 2! + ... + 50 x 50! equals

• 51!

• 51! + 1

• 51! + 1

• 2 $\times$ 51!

Six numbers are in AP such that their sum is 3. The first term is 4 times the third term. Then, the fifth term is

• - 15

• - 3

• 9

• - 4

The sum of the infinite series $1 +\hspace{0.17em}\frac{1}{3} + \frac{1 . 3}{3 . 6} +\hspace{0.17em}\frac{1 . 3 . 5}{3 . 6 . 9} + \frac{1 . 3 . 5 . 7}{3 . 6 . 9 . 12} + ...$ is equal to

• $\sqrt{2}$

• $\sqrt{3}$

• $\sqrt{\frac{3}{2}}$

• $\sqrt{\frac{1}{3}}$

If 64, 27, 36 are the Pth Qth and Rth terms of a GP, then P + 2Q is equal to

• R

• 2R

• 3R

• 4R

77.

Let a, b, c, p, q and r be positive real numbers such that a, band c are in GP and a^p = b^q = c^r . Then,

• p, q, r are in GP

• p, q, r are in AP

• p, q, r are in HP

• p², q², r² are in AP

Let S_k be the sum of an infinite GP series whose first term is k and common ratio is $\frac{\mathrm{k}}{\mathrm{k} + 1}$(k > 0). Then, the value of $\sum _{\mathrm{k} = 1}^{\infty } \frac{\left(- 1\right)}{{\mathrm{S}}_{\mathrm{k}}}$ is equal to

• ${\log }_{\mathrm{e}}\left(4\right)$

• ${\log }_{\mathrm{e}}\left(2\right) - 1$

• 1 - ${\log }_{\mathrm{e}}\left(2\right)$

• 1 - ${\log }_{\mathrm{e}}\left(4\right)$

The harmonic mean of two numbers is 4. Their arithmetic mean A and geometric mean G satisfy the relation 2A +G² = 27. Find the numbers.

The sum of the series $\frac{1}{1 . 2} - \frac{1}{2 . 3} + \frac{1}{3 . 4} - ... \infty$

• $2{\log }_{\mathrm{e}}\left(2\right) + 1$

• $2{\log }_{\mathrm{e}}\left(2\right)$

• $2{\log }_{\mathrm{e}}\left(2\right) - 1$

• ${\log }_{\mathrm{e}}\left(2\right) - 1$