Question

Tính:

B =1 + 3 + 3²  + 3³ + ......+ 3⁵⁰

Answer 1

B = 1 + 3 + 3^2 + 3^3 + ....+ 3^50

3B= 3+3^2+3^3+3^4+....+3^51

3B-B=(3+3^2+3^3+3^4+....+3^51)-(1+3+3^2+3^3+....+3^50)

2B=3^51-1

=> B=(3^51-1) : 2

Ủng hộ mik nhé !

Answer 2

B=\(1+3+3^2+...+3^{50}\)

3B=\(3+3^2+...+3^{51}\)

3B-B=\(\left(3+3^2+3^3+...+3^{51}\right)-\left(1+3+3^2+...+3^{50}\right)\)

2B=2+3^51

B=\(\frac{2+3^{51}}{2}\)

Answer 3

\(3B=3+3^2+3^3+...+3^{51}\)

\(3B-B=\left(3+3^2+...+3^{51}\right)-\left(1+3+3^2+...+3^{50}\right)\)

\(2B=3^{51}-1\)

\(B=\frac{3^{51}-1}{2}\)