\(A=\dfrac{1}{4}+\dfrac{1}{16}+...+\dfrac{1}{576}\)
=1/2^2(1+1/2^2+...+1/12^2)
1/2^2+1/3^2+...+1/12^2<1-1/2+1/2-1/3+...+1/11-1/12=11/12
=>1+1/2^2+1/3^2+...+1/12^2<1+11/12=23/12
=>A<23/12*1/4=23/48<23/46=1/2
Chứng tỏ rằng:A=1/4+1/16+1/36+1/64+...+1/576<1/2
Chứng minh rằng: A=1/4+1/16+1/36+1/64+...+1/576<1/2
Chứng minh A = 1/4 + 1/6 + 1/36 + ....... + 1/576 < 1/2
CMR:
1/4+1/16+1/36+....+1/10000<1/2
CMR : 1/4 + 1/16 + 1/36 + 1/64 + 1/100 + 1/144 + ... + 1/10000 < 1/2
chung to A=1/4+1/16+.....+1/576<1/2
S = 1/4 + 1/9 + 1/16 + 1/25 + 1/36 + 1/49 + 1/64 + 1/81
CMR: 2/2 < S < 8/9
Tính:
A=1*2*3+2*3*4+3*4*5+......+98*99*100
CMR:
A=1/4+1/16+1/36+1/64+1/100+1/144+1/196<1/2
CMR:
(1/4+1/16+1/36+1/68+1/1001/144+1/196)<1/5+1/4+1/20
