a) \(B=5+5^2+5^3+...+5^{2022}\)
\(\Rightarrow5B=5^2+5^3+5^4+...+5^{2023}\)
\(\Rightarrow4B=5^{2023}-5\)
b) \(4B+5=5^X\)
Hay \(5^{2023}-5+5=5^X\)
\(5^{2023}=5^x\)
\(\Rightarrow x=2023\)
B = 5 + 52 + 53 +...+ 52022
5.B = 52 + 53 +....+ 52023
5B- B = 52023 - 5
4B = 52023 - 5
b, 4B + 5 = 5\(^x\) ⇒ 52023 - 5 + 5 = 5\(^x\)
5\(^{2023}\) = 5\(x\)
\(x\) = 2023
Nguyễn Thị Thương Hoài
Cô ơi, x = 2023 vì x nằm ở mũ nha cô.
a) \(B=5+5^2+5^3+...+5^{2022}\)
\(\Rightarrow5B=5^2+5^3+5^4+...+5^{2023}\)
\(\Rightarrow4B=5B-B\)
\(=\left(5^2+5^3+5^4+...+5^{2023}\right)-\left(5+5^2+5^3+...+5^{2022}\right)\)
\(=5^{2023}-5\)
\(\Rightarrow B=\dfrac{5^{2023}-5}{4}\)
b) \(B=\dfrac{5^{2023}-5}{4}\)
\(\Rightarrow4B=4.\dfrac{5^{2023}-5}{4}=5^{2023}-5\)
\(\Rightarrow4B+5=5^{2023}-5+5=5^{2023}\)
Mà \(4B+5=5^x\)
\(\Rightarrow5^x=5^{2023}\)
\(\Rightarrow x=2023\)