Question

[jack killer]

tính D=1-3+3^2-3^3+3^4-3^5+...+3^98-3^99+3^100

nhờ các bạn giải nhanh giúp mk

Answer 1

[•♡๖ۣۜLê☠๖ۣۜNɠọ¢☠๖ۣۜTυүềη☠(☠๖ۣۜTεαм☠...]

\(D=1-3+3^2-3^3+3^4-3^5+...+3^{98}-3^{99}+3^{100}\)

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

\(3D=3-3^2+3^3-3^4+3^5-3^6+...+3^{99}-3^{100}+3^{101}\)

\(3D+D=\left(3-3^2+3^3-3^4+3^5-3^6+...+3^{99}-3^{100}+3^{101}\right)\)

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

\(4D=3^{101}+1\)           \(\Rightarrow D=\frac{3^{101}+1}{4}\)

Answer 2

[jack killer]

cảm ơn nha