Tìm \(n\) thỏa mãn \(C^n_n+C^{n-1}_n+C^{n-1}_n+.......+C^1_n=127\).
n = 7 n = 8 n = 1 n = 2 Hướng dẫn giải:\(C^n_n+C^{n-1}_n+C^{n-1}_n+.......+C^1_n=127\) \(\Leftrightarrow C^n_n+C^{n-1}_n+C^{n-1}_n+.......+C^1_n+C^0_n=128\) \(\Leftrightarrow2^n=2^7\) \(\Leftrightarrow n=7\).
