Question

tính giá trị biểu thứ 4S-3^2023
biết S = 1+3+3^2+...+3^2022     

Answer 1

\(S=1+3+3^2+...+3^{2022}\\ 3S=3+3^2+3^3+...+3^{2023}\\ 3S-S=\left(3+3^2+3^3+...+3^{2023}\right)-\left(1+3+3^2+...+3^{2022}\right)\\ 2S=3^{2023}-1\\4S=\dfrac{3^{2023}\times2-1\times2}{2}\\ 4S=\dfrac{\left(3^{2023}-1\right)\times2}{2}\\ 4S=3^{2023}-1\\ 4S-3^{2023}=3^{2023}-1-3^{2023}\\ 4S-3^{2023}=\left(-1\right)\)