So sanh
1/41 +1/42 + 1/4+1/43+...+1/79 va 7/12
lam nhanh minh tick
Những câu hỏi liên quan
1/41+1/42+1/43+...+1/79 va 7/12( So sanh )
lam nhanh minh tick cho5 cai nha
ta có
7/12 = 4/12 +3 /12 = 1/3 + 1/4 = 20/60 + 20/80
1/41 + 1/42 + 1/43 + ....+ 1/79 + 1/80 = ( 1/41 + 1/42 + 1/43 + ...+1/60 ) + ( 1/61 + 1/62 + 1/63 + ...+ 1/79 + 1/80 )
do 1/41 > 1/42 > 1/43 > ... > 1/59 > 1/60
( 1/41 + 1/42 + 1/43 +...+ 1/60 ) > 1/60 + ..+ 1/60 = 20/60
và 1/61 >1/62>..1/80
( 1/61 + 1/62 + 1/63 + ...+ 1/80 ) > 1/80 +....+1/80 = 20/80
vậy 1/41 + 1/42 + 1/43 + .... + 1/79 + 1/80 > 20/60 + 20/80
1/41 + 1/42 + 1/43 + ..... + 1/79 + 1/80 > 7/12
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so sanh c va 5/6
c = 1/41+1/42+1/43+...+1/80
Chứng minh:7/12< 1/41+1/42+1/43+...+1/79+1/80<1
A<10(1/40+1/50+1/70+1/60)=319/420<1
A>10(1/50+1/60+1/70+1/80)>7/12
=>7/12<A<1
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Chứng minh rằng: 1/41+1/42+1/43+..........+1/79+1/80>7/12
A=1\41+1\42+1\43+...+1\79+1\80.chung minh A >7\12
Chững minh rằng : 1/41 + 1/42 + 1/43 +... + 1/79 + 1/80 > 7/12
Chứng minh rằng: 1/41+1/42+1/43+...+1/79+1/80 >7/12
so sanh A=\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{80}\)va B=\(\frac{7}{12}\)
Chứng minh rằng :
1/41 + 1/42 + 1/43 + ... + 1/79 + 1/80 > 7/12