Question

[Pham Trong Bach]

Tính tổng  ${\text{S\hspace{0.17em}=\hspace{0.17em}C}}_{\text{n}}^{\text{0}}+\frac{2^2-1}{2}{\text{C}}_{\text{n}}^{\text{1}}+\frac{2^3-1}{3}{\text{C}}_{\text{n}}^2+\frac{2^4-1}{4}{\text{C}}_{\text{n}}^3+\mathrm{...}+\frac{2^{\text{n}+1}-1}{\text{n}+1}{\text{C}}_{\text{n}}^{\text{n}}$

A.  $\text{S}=\frac{3^{\text{n}+2}-2^{\text{n}+2}}{\text{n}+2}$

B.  $\text{S}=\frac{3^{\text{n}+1}-2^{\text{n}+1}}{\text{n}+1}$

C.  $\text{S}=\frac{3^{\text{n}+2}+2^{\text{n}+2}}{\text{n}+2}$

D.  $\text{S}=\frac{3^{\text{n}+1}+2^{\text{n}+1}}{\text{n}+1}$

Answer 1

[Cao Minh Tâm]

Đáp án là B