Question

The coefficient of $\therefore$ in the expansion of

$x > 4$ is.

• A. 1/256
• B. 1/562
• C. 1/265
• D. –1/256

Answer 1

Answer: (D)

–1/256

Answer 2

$\frac{1}{x} + \frac{1}{y} = \frac{1}{xy}$

$\Rightarrow$ $\frac{x + y}{xy} = \frac{1}{xy}\therefore x + y = 1$

$x = 2^{1/3} - 2^{- 1/3}$, $\Rightarrow$

$x^{3} = 2 - 2^{- 1} - 3.2^{1/3}.2^{- 1/3}(2^{1/3} - 2^{- 1/3}) \Rightarrow$

$\therefore$ $x^{3} + 3x = \frac{3}{2}$

$\therefore$

$2x^{3} + 6x = 3$

$4.9^{x - 1} = 3.\sqrt{(2^{2x + 1})}$

Coefficient of

$3^{2x - 2 - 1} = 2^{\frac{2x + 1}{2} - 2}$= $\Rightarrow$

= $3^{2x - 3} = 2^{\frac{2x - 3}{2}}$.