chung minh rang A=1/11×1/12×1/13+...+1/50>1/3
Những câu hỏi liên quan
Chung minh rang : 1/11+1/12+1/13+...+1/50 < 8/5
Cho S= 3/1+3/11+3/12+3/13+3/14
Chung minh rang 1<S<2
* S = 3/10+3/11+3/12+3/13+3/14 < 3/10 + 3/10+3/10+3/10+3/10
< 3/10 x 5
< 3/2 < 2sư
* S = 3/10+3/11+3/12+3/13+3/14 > 3/15+3/15+3/15+3/15+3/15
> 3/15 x 5
> 1
CHỨNG TỎ ........
> 1
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So sanh phan so 1313/9191va1111/7373
Chung minh rang
A=1/12+1/13+.....+1/22>1/2
B=1/10+1/11+.....+1/99+1/100>1
C=1/5+1/6+1/7+....+1/17<2
D=3/10+3/11+3/12+3/13+3/14
Hoi d co la so tu nhien ko
Cam on cac ban rat nhieu
Chung to rang A=1/8+1/11+1/12+1/13+1/41+1/42+1/43 <1/2
\(\frac{1}{8}=\frac{1}{8}\)
\(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}<\frac{3}{10}\)
\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}<\frac{3}{40}\)
-> A <\(\frac{1}{8}+\frac{3}{10}+\frac{3}{40}=\frac{20}{40}=\frac{1}{2}\)
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chung minh A=1/11+1/12+...+1/50<8/3
a,A=1/1^2+1/2^2+1/3^2+1/4^2+...+1/50^2.chung minh rang a<2
b;2^1+2^2+2^3+...+2^30.chung minh rang B chia het cho21
chung minh rang 11^n+2+12^2n+1 chia het cho 133
chung minh rang A=(17^n+1)(17^n+2)chia het cho 3 voi moi n thuoc N
cho (2a+7b) chia het cho 3 ( a b thuoc N). chung to (4a+2b) chia het cho 3
cho C = 1 +3 + 32 + 33 + .... + 311 chung minh rang
a, chứng minh rằng C chia hết cho 13
b, chung minh rang C CHIA HET CHO 40
cho a=1=1\2+1\3-1\4+1\5...+1\49-1\50.Chung to rang 7\12<4<5\6