\(\frac{1}{8}=\frac{1}{8}\)
\(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}<\frac{3}{10}\)
\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}<\frac{3}{40}\)
-> A <\(\frac{1}{8}+\frac{3}{10}+\frac{3}{40}=\frac{20}{40}=\frac{1}{2}\)
chứng tỏ rằng :\(\frac{1}{8}+\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+\frac{1}{41}+\frac{1}{42}+\frac{1}{43}< \frac{1}{2}\)
chung to :1/41+1/42+1/43+.....+1/80>7/12
A=1\41+1\42+1\43+...+1\79+1\80.chung minh A >7\12
tính tổng sau
1-2-3+4-5-6+7+8-9-10+11+12-13-14-15+..+40-42+41-43
Tính : a, S = 1+4+7+10+13+......+301 b,S= 1+5+9+13+.....+ .... c, S= 1+2-3-4+5+6-7-8+9+10-11-12+..... +41+42-43-44 d, S= 2.1+2.2+2.3+2.4+....+2.99 mình đang can khan cap nho cac ban lam cho minh ti voi
Chứng minh rằng:
a)A=1/11+1/12+1/13+...+1/20>1/2 b)B=1/41+1/42+1/43+...+1/80>7/20
chứng tỏ:
1/8+1/11+1/12+1/13+141+1/42+1/43< 1/2
giúp mình nha cần gấp đó
Chung to
rang:a,1/41+1/42+1/43+....+1/80>1/2 b,1/3+1/3^2+1/3^3+....+1/3^99<1/2
chung minh rang A=1/11×1/12×1/13+...+1/50>1/3
