\(D=\frac{19^{17}\left(1+19\right)}{19^{18}\left(1+19\right)}=\frac{1}{19}\)
\(D=\frac{19^{17}\left(1+19\right)}{19^{18}\left(1+19\right)}=\frac{1}{19}\)
tim D=\(\frac{\frac{1}{19}+\frac{2}{18}+\frac{3}{17}+.....+\frac{18}{2}+\frac{19}{1}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+.....+\frac{1}{19}+\frac{1}{20}}\)
Cho \(S=\frac{17}{18}+\frac{18}{19}+\frac{19}{20}+\frac{20}{17}\)
SO sánh S với 4
Tính A=\(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}}{\frac{19}{1}+\frac{18}{2}+\frac{17}{3}+...+\frac{3}{17}+\frac{2}{18}+\frac{1}{19}}\)
\(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}}{\frac{19}{1}+\frac{18}{2}+\frac{17}{3}+...+\frac{3}{17}+\frac{2}{18}+\frac{1}{19}}\)
chứng minh rằng:\(\frac{17^{18}+1}{17^{19}+1}< \frac{17^{18}+1+16}{17^{19}+1+16}\)
17+18+19+...99 bằng bao nhiêu?
Bài 1: Tính
\(\frac{\frac{1}{19}+\frac{2}{18}+\frac{3}{17}+....+\frac{18}{2}+\frac{19}{1}}{\frac{1}{2}+\frac{1}{3}+....+\frac{1}{19}+\frac{1}{20}}\)
Tính hợp lí:
17 (18 + 19) + 12 (18 + 19) - 18 - 19
Hiệu ( 1 . 2 . 3 . 4 ...... 17 . 18 . 19 ) - ( 1 . 3 . 5 . 7 ...... 17 . 19 ) có chữ số tận cùng là bao nhiêu ?