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
chung to rang 1/2^2+1/3^2+1/4^2+....+1/100^2 <1
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+1/2+1/3+...+1/2^100-1
chung minh rang:
a,A<100
b,A>50
Chung to rang:1+1/2 mu2+1/3 mu2+1/4 mu2+....+1/100 mu2 be hon 2
chung to rang:
1 + 2^2 + 2^3 + 2^4 +.....+ 2^100 = 2^101 - 1
