Question

tính tổng:B=1+7+7 mũ 2+7 mũ 3+7 mũ 4+...+7 mũ 50

Answer 1

B = 1 + 7 + 7² + 7³ + .. + 7⁵⁰ 

7B = 7 + 7² + 7³ + ... + 7⁵¹ 

7B-B = 7⁵¹ - 1 

6B = 7⁵¹ - 1 

B = \(\frac{7^{51}-1}{6}\)

Study well 

Answer 2

                                                      Bài giải

\(B=1+7+7^2+7^3+7^4+...+7^{50}\)

\(7B=7+7^2+7^3+7^4+7^5+...+7^{51}\)

\(7B-B=6B=7^{51}-1\)

\(B=\frac{7^{51}-1}{6}\)

Answer 3

\(B=1+7+7^2+7^3+7^4+...+7^{50}\)

\(7B=7+7^2+7^3+7^4+7^5+...+7^{51}\)

\(7B-B=6B=7^{51}-1\)

\(B=\frac{7^{51}-1}{6}\)