Câu hỏi của Quyên Lê

Question

A=1-5+5²-5³+....+5⁹⁸-5⁹⁹

Nguyễn Huy Tú · Accepted Answer

$A=1-5+5^2-5^3+...+5^{98}-5^{99}$

$\Rightarrow5A=5-5^2+5^3-5^4+...+5^{99}-5^{100}$

$\Rightarrow5A+A=\left(5-5^2+5^3-5^4+...+5^{99}-5^{100}\right)+\left(1-5+5^2-5^3+...+5^{98}-5^{99}\right)$$\Rightarrow6A=1-5^{100}$

$\Rightarrow A=\dfrac{1-5^{100}}{6}$

Câu trả lời:

$A=1-5+5^2-5^3+...+5^{98}-5^{99}$

$\Rightarrow5A=5-5^2+5^3-5^4+...+5^{99}-5^{100}$

$\Rightarrow5A+A=\left(5-5^2+5^3-5^4+...+5^{99}-5^{100}\right)+\left(1-5+5^2-5^3+...+5^{98}-5^{99}\right)$$\Rightarrow6A=1-5^{100}$

$\Rightarrow A=\dfrac{1-5^{100}}{6}$

Đức Hiếu · Answer

Ta có:

$A=1-5+5^2-5^3+.....+5^{98}-5^{99}$

$\Rightarrow5A=5-5^2+5^3-5^4+......+5^{99}-5^{100}$

$\Rightarrow5A+A=\left(5-5^2+5^3-5^4+.......+5^{99}-5^{100}\right)+\left(1-5+5^2-5^3+......+5^{98}-5^{99}\right)$

$\Rightarrow6A=-5^{100}+1$

$\Rightarrow A=\dfrac{1-5^{100}}{6}$

Chúc bạn học tốt!!!

Câu trả lời:

Ta có:

$A=1-5+5^2-5^3+.....+5^{98}-5^{99}$

$\Rightarrow5A=5-5^2+5^3-5^4+......+5^{99}-5^{100}$

$\Rightarrow5A+A=\left(5-5^2+5^3-5^4+.......+5^{99}-5^{100}\right)+\left(1-5+5^2-5^3+......+5^{98}-5^{99}\right)$

$\Rightarrow6A=-5^{100}+1$

$\Rightarrow A=\dfrac{1-5^{100}}{6}$

Chúc bạn học tốt!!!