Question

B=3+3 mũ 2 + 3 mũ 3 +.......+3 mũ 50 đề bài rút gọn

Answer 1

B=3+3²+3³+...+3⁵⁰

3B=3²+3³+...+3⁵¹

3B-B=(3²+3³+...+3⁵¹)-(3+3²+3³+...+3⁵⁰)

2B=3⁵¹-3

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

Answer 2

B=3+3²+3³+...+3⁵⁰

3B=3²+3³+...+3⁵¹

3B-B=(3²+3³+...+3⁵¹)-(3+3²+3³+...+3⁵⁰)

2B=3⁵¹-3

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

Answer 3

\(B=3+3^2+3^3+...+3^{50}\\ 3B=3^2+3^3+3^4+...+3^{51}\\ 3B-B=\left(3^2+3^3+3^4+...+3^{51}\right)-\left(3+3^2+3^3+...+3^{50}\right)\\ 2B=3^{51}-3\\ \Rightarrow B=\dfrac{3^{51}-3}{2}\)

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