Practice By Tag: Newton's Binomial Theorem

Question: 2017 Fall Midterm - 9

1 . What is the coefficient of $x^{20}y^{80}$ in the expansion of $(7x-13y)^{100}$?

(a)

${100 \choose 20} \cdot 7^{80} \cdot 13^{20}$

(b)

${100 \choose 80} \cdot 7^{20} \cdot 13^{80}$

(c)

$- {100 \choose 20} \cdot 7^{80} \cdot 13^{20}$

(d)

$- {100 \choose 80} \cdot 7^{20} \cdot 13^{80}$