Question

In the expansion of $(x-1)(x-2)....(x-18)$, the coefficient of $x^{17}$ is

• A. $684$
• B. $-171$
• C. $171$
• D. $-342$

Answer 1

Answer: (B)

Coefficient of $x^{17}$ is: $-\left(1+2+3+.......+18\right)=-\left(\frac{18\times 19}{2}\right)=-171$