Question Number 22517 by Tinkutara last updated on 19/Oct/17
![Find the coefficient of x in the expansion of [(√(1 + x^2 )) − x]^(−1) in ascending power of x when ∣x∣ < 1.](Q22517.png)
$$\mathrm{Find}\:\mathrm{the}\:\mathrm{coefficient}\:\mathrm{of}\:{x}\:\mathrm{in}\:\mathrm{the}\:\mathrm{expansion} \\ $$ $$\mathrm{of}\:\left[\sqrt{\mathrm{1}\:+\:{x}^{\mathrm{2}} }\:−\:{x}\right]^{−\mathrm{1}} \:\mathrm{in}\:\mathrm{ascending}\:\mathrm{power} \\ $$ $$\mathrm{of}\:{x}\:\mathrm{when}\:\mid{x}\mid\:<\:\mathrm{1}. \\ $$