Question

The term independent of $x$ in the expansion of ${\left(x-\frac{1}{x}\right)}^4{\left(x+\frac{1}{x}\right)}^3$ is :

• A. -3
• B. 0
• C. 1
• D. 3

Answer 1

Answer: (B)

$\left({}^4{C}_0{x}^4-{}^4{C}_1{x}^2+{}^4{C}_2-4C_3\frac{1}{x^2}+{}^4{C}_4\frac{1}{x^4}\right)\left(x^3+3x+\frac{3}{x}+\frac{1}{x^3}\right)\Rightarrow$ coefficient of $x$ is 0