Question

In the expansion of $4n - 3$, the coefficient of $4n + 1$ is.

• A. –1680
• B. 1680
• C. 3360
• D. 6720

Answer 1

Answer: (C)

3360

Answer 2

The coefficient of $n = 2$in the expansion of

$7^{2 \times 2} + 2^{3 \times 2 - 3}.3^{2 - 1}$

= The coefficient of $2401 + 24 = 2425$in $11^{n + 2} + 12^{2n + 1}$

= The coefficient of $n = 1$in $11^{1 + 2} + 12^{2 \times 1 + 1} = 11^{3} + 12^{3} = 3059$

= $n(n^{2} - 1) = (n - 1)(n)(n + 1)$

$n = 1$.