a) Rút gọn:\(\frac{\frac{1}{1\cdot300}+\frac{1}{2\cdot301}+\frac{1}{3\cdot302}+...+\frac{1}{101\cdot400}}{\frac{1}{1\cdot102}+\frac{1}{2\cdot103}+\frac{1}{3\cdot104}+...+\frac{1}{299\cdot400}}\)b) CMR: \(1\cdot3\cdot5\cdot7\cdot9\cdot...\cdot197\cdot199\)= \(\frac{101}{2}\cdot\frac{102}{2}\cdot\frac{103}{2}\cdot...\cdot\frac{200}{2}\).c) Cho: A=\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{199\cdot200}\). ...
Đọc tiếp
a) Rút gọn:
\(\frac{\frac{1}{1\cdot300}+\frac{1}{2\cdot301}+\frac{1}{3\cdot302}+...+\frac{1}{101\cdot400}}{\frac{1}{1\cdot102}+\frac{1}{2\cdot103}+\frac{1}{3\cdot104}+...+\frac{1}{299\cdot400}}\)
b) CMR: \(1\cdot3\cdot5\cdot7\cdot9\cdot...\cdot197\cdot199\)= \(\frac{101}{2}\cdot\frac{102}{2}\cdot\frac{103}{2}\cdot...\cdot\frac{200}{2}\).
c) Cho: A=\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{199\cdot200}\).
B=\(\frac{1}{101\cdot200}+\frac{1}{102\cdot199}+...+\frac{1}{199\cdot102}+\frac{1}{200\cdot101}\).
d) Tìm số tự nhiên n lớn nhất có ba chữ số sao cho n chia 8 dư 7,chia 31 dư 28.
e) Tìm số nguyên tố \(\overline{ab}\) (a>0>b),sao cho \(\overline{ab}-\overline{ba}\)là số chính phương.
