Question

thu gọn : 1+3 mũ 1 + 3 mũ 2 +.....+3 mũ 50

Answer 1

giúp tôi với please

Answer 2

Đặt \(A=1+3^1+3^2+...+3^{50}\)

=>\(3\cdot A=3+3^2+3^3+...+3^{51}\)

=>\(3A-A=3+3^2+3^3+...+3^{51}-1-3^1-...-3^{50}\)

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

=>\(A=\dfrac{3^{51}-1}{2}\)