Question

A=1+3+3^2+3^3+....+3^10
B=1+5+5^2+5^3+...+5^20
Ai làm nhanh mk tick <3

Answer 1

A=88573

phan B to lam khoang tam 14 chu so tran man hinh mt vinacal, mik k tinh dk

Answer 2

Làm rõ ràng mk k cho :)

Answer 3

mik dùng máy tính vinacal để tính

Answer 4

Ta có
\(A=1+3+3^2+3^3+...+3^{10}\)
\(3A=3+3^2+3^3+3^4+...+3^{11}\)
\(2A=3A-A=3^{11}-1\)
\(\Rightarrow A=\frac{3^{11}-1}{2}\)
\(B=1+5+5^2+5^3+...+5^{20}\)
\(5B=5+5^2+5^3+5^4+...+5^{21}\)
\(4B=5B-B=5^{21}-1\)
\(\Rightarrow B=\frac{5^{21}-1}{4}\)