Chung to :1/2 + 1/3 + 1/4 +...+1/9 <2
Chung to :1/2 + 1/3 + 1/4 +...+1/9 <2
Đặt A=1/2+1/3+1/4+...+1/9
A=(1/2+1/3)+(1/4+1/5)+(1/6+1/7)+(1/8+1/9)
A<1/2+1/3+1/4+1/4+1/6+1/6+1/8+1/8
A<5/6+1/2+1/3+1/4
A<23/12<24/12=2
Nên A<2
Chứng tỏ rằng: 1/3^2+1/4^2+1/5^2+...+1/60^2<4/9
kho vler ai biet thi tra loi gium!
Cho A=1/3^2+1/4^2+1/5^2+...+1/50^2
Chung to rang a,A>1=4 b,A>4/9
Cho A=1/3^2+1/4^2+1/5^2+...+1/50^2
Chung to rang 1/4<M<4/9
Cho A=1/3^2+1/4^2+1/5^2+...+1/50^2
Chung to rang 1/4<M<4/9
Cho A=1/3^2+1/4^2+1/5^2+...+1/50^2
Chung to rang a,A>1=4 b,A>4/9
Cho A=1/3^2+1/4^2+1/5^2+...+1/50^2
Chung to rang 1/4<M<4/9
tim so tu nhien x,y sao cho:x /9 -3 / y = 1 / 18
cho A= 1/1^2 + 1/2^2+1/3^2 1/4^2+...+1/50^2. chung minhA<2
tinh tong S=3+3/2+3/2^2+...3/2^9
ban nao giup voi nhe to can on truoc
\(\frac{1}{1^2+2^2}+\frac{1}{2^2+3^2}+\frac{1}{3^2+4^2}+.....+\frac{1}{10^2+11^2}< \frac{9}{20}\)
1/12+22 + 1/22+32 + 1/32+42 + ... + 1/102+112
< 1/12+12 + 1/22+22 + 1/32+32 + ... + 1/102+102
< 1/2.12 + 1/2.22 + 1/2.32 + ... + 1/2.102
< 1/2.(1/12 + 1/22 + 1/32 + ... + 1/102)
< 1/2.(1 + 1/1.2 + 1/2.3 + ... + 1/9.10)
< 1/2.(1 + 1 - 1/2 + 1/2 - 1/3 + ... + 1/9 - 1/10)
< 1/2.(2 - 1/10)
< 1/2.(20/10 - 1/10)
< 1/2.19/10
< 19/20
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