Xét riêng cái biểu thức trong ngoặc nhé, đặt là B :
B = 1/6+1/24+1/60+...+1/9240
B = 1/1x2x3+1/2x3x4+1/3x4x5+...+1/20x21x22
B = (1/1x2 - 1/2x3) : 2 + (1/2x3-1/3x4) : 2 + (1/3x4 - 1/4x5) : 2 +...+ (1/20x21 - 1/21x22) : 2
B = (1/1x2-1/2x3+1/2x3-1/3x4+1/3x4-...-1/21x22) : 2
B = (1/2 - 1/462) : 2
B = 115/462
=> A = 1/2 x 115/462 > 1/2 x 114/462 = 57/462 (đpcm)
Chứng minh rằng A=1/2(1/6+1/24+1/60+....+1/9240)>57/462
chứng minh rằng : A=1/2.(1/6+1/24+1/60+...+1/9240)>57/462
Chứng minh rằng : A=1/2.(1/6+1/24+1/60+...+1/9240)>57/462
Chứng minh A=1/2.(1/6+1/24+1/60+...+1/9240) > 57/46
Chứng minh: A = \(\frac{1}{2}.\left(\frac{1}{6}+\frac{1}{24}+\frac{1}{60}+...+\frac{1}{9240}\right)>\frac{57}{462}\)
Trình bày luôn cách giải
chung minh rang a=1/2.(1/6+1/24+1/60+...+1/9240)>57/462
Chứng minh : A = \(\frac{1}{2}\left(\frac{1}{6}+\frac{1}{24}+\frac{1}{60}+...+\frac{1}{9240}\right)>\frac{57}{462}\)
Chứng minh A= \(\frac{1}{2}\left(\frac{1}{6}+\frac{1}{24}+\frac{1}{60}+...+\frac{1}{9240}\right)>\frac{57}{462}\)
Chứng minh A= \(\frac{1}{2}\left(\frac{1}{6}+\frac{1}{24}+\frac{1}{60}+...+\frac{1}{9240}\right)>\frac{57}{462}\)
