Question

The sum of the co-efficients of all odd degree terms in the expansion of ${(x+\sqrt{x^3-1})}^5+{(x+\sqrt{x^3-1})}^5$
$(x>1)$ is:

• A. $2$
• B. $-1$
• C. $0$
• D. $1$

Answer 1

Answer: (A)

$2$

Sum of the coefficient of odd term is given by

$=2[{}^5{C}_0+{}^5{C}_2+{}^5{C}_4]$

$=2[1+10-10+5-10+5]$

$=2(1+5+5-10)$

$=2$.