Đặt \(A=\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{20}\)
\(A>\frac{1}{20}+\frac{1}{20}+\frac{1}{20}+...+\frac{1}{20}\) ( 19 số hạng )
\(A>\frac{19}{20}\)
So sánh 1/2 + 1/3 + 1/4 + ... + 1/18 + 1/19 + 1/20 và 19/20
C=1/1*2*3*4+1/3*4*5+...+1/17*18*19+1/18*19*20
Tinh:
1/19 + 2/18 + 3/17 +...+ 18/2 + 19/1
1/2 + 1/3 + 1/4 +...+ 1/19 + 1/20
tinh : (1/19+2/18+3/17+...+18/2+19/1)/1/2+1/3+1/4+...+1/20
Tính :
(1/19+2/18+3/17+...+18/2)/1/2+1/3+1/4+...+1/19+1/20
so sánh:
A=17^18+1/17^19+1 và B=17^17+1/17^18+1
gấp^2
1/2+1/3+1/4+....+1/19+1/20
19/1+18/2+17/3+....+2/18+1/19
Bạn nào giúp giải ra chi tiết luôn nhé. Thank nhiều.
Tính A=\(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}}{\frac{19}{1}+\frac{18}{2}+\frac{17}{3}+...+\frac{3}{17}+\frac{2}{18}+\frac{1}{19}}\)
\(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}}{\frac{19}{1}+\frac{18}{2}+\frac{17}{3}+...+\frac{3}{17}+\frac{2}{18}+\frac{1}{19}}\)
