Question Number 6895 by Chheang Chantria last updated on 02/Aug/16
Commented by Chheang Chantria last updated on 02/Aug/16
$$\mathrm{help}\:\mathrm{me}\:\mathrm{excercise}\:“\:\mathrm{d}'' \\ $$
Answered by sou1618 last updated on 02/Aug/16
$${D}=\underset{{k}=\mathrm{0}} {\overset{{n}} {\sum}}\left(−\mathrm{1}\right)^{{k}} {C}\left({n},{k}\right)\mathrm{2}^{{n}−{k}} \mathrm{3}^{{k}} \\ $$$${D}=\underset{{k}=\mathrm{0}} {\overset{{n}} {\sum}}{C}\left({n},{k}\right)\mathrm{2}^{{n}−{k}} \left(−\mathrm{3}\right)^{{k}} \\ $$$${D}=\left(\mathrm{2}−\mathrm{3}\right)^{{n}} \\ $$$${D}=\left(−\mathrm{1}\right)^{{n}} \\ $$