Question

The term independent of x in the product (4 + x + 7x²)$\left( x–\frac{3}{x} \right)^{11}$is

• A. 7 .¹¹C₆
• B. 3⁶ .¹¹C₆
• C. 3⁵.¹¹C₅
• D. –12 . 2¹¹

Answer 1

Answer: (B)

3⁶ .¹¹C₆

Answer 2

General term of $\left( x–\frac{3}{x} \right)^{11}$

T_r+1 = ¹¹C_r x^{11– r} $\left( –\frac{3}{x} \right)^{r}$ = ¹¹C_r x^11–2r (–3)^r

11 – 2r ¹ 0, –2 so 11 – 2r = –1 is only possible case r = 6

Ž (–3)^{6 11}C₆