A = (1/31+1/32+1/33+...+1/40) + (1/41 + 1/42 + ...+ 1/50) + (1/51 + 1/52+...+1/59+1/60)
Mà : (1/31+1/32+1/33+...+1/40) < 1/31 x 10 = 10/30 = 1/3 (gồm 10 số hạng)
Tương tự : (1/41 + 1/42 + ...+ 1/50) < 1/4 ; (1/51 + 1/52+...+1/59+1/60) < 1/5
Mà A = (1/3 + 1/4 + 1/5) = 47/60 > 7/12
Vậy A >7/12
cho A= 1/31+1/32+1/33+.....+1/60
chứng minh rằng A> 7/12
Cho:A=1/31+1/32+1/33+..............+1/60
Chứng minh rằngA>7/12
cho \(A=\frac{1}{31}+\frac{1}{32}+\frac{1}{33}+...+\frac{1}{60}\)
chứng minh rằng \(A>\frac{7}{12}\)
cho A = 1/31 + 1/32 + 1/33 + ... + 1/60 CMR : A > 7/12
cho A= 1/31+1/32+1/33+...+1/60
chứng minh 3/5<A<4/5
chưgs minh rằng :
1/31+1/32+1/33+.....+1/60>7/12
Chứng tỏ rằng
7/12<1/31+1/32+1/33+... +1/59+1/60<5/6
PLEASE, HELP ME
Cho S = 1/31+1/32+1/33+.......+1/60.Chứng minh 3/5 < S < 4/
a, tính a= 2/1.3+2/3.5+2/5.7+2/7.9+...+2/2017.2019
b, cho S= 1/31+1/32+1/33...+1/60. chứng minh S<4/5
chú ý / là phần
