CM: 41/2×42/2×43/2×.....×80/2=1×3×5×....×79
CMR 1/41+1/42+1/43+...+1/79+7/80 <7/12
Cmr 1/41+4/42+4/43+.........+1/79+1/80>7/12
CMR : a) 1/41 + 1/42 + 1/43 +...+ 1/80 < 5/6
b) 1/2^2 + 1/2^4 + 1/2^6 +...+ 1/2^200 < 1/3
Chứng minh rằng
a) 1/2 + 1/3 + 1/4 +...+1/63 > 2
b) 1/41 + 1/42 + 1/43 +...+1/79 + 1/80 > 7/12
Chứng tỏ rằng : 7/12 < 1/41 + 1/42 +...+1/79+1/80<5/6
1,Chứng minh rằng:
1/2<1/51+1/52+...+1/100<1
2,Chứng minh 1/41+1/42+1/43+...+1/79+1/80>7/12
Hãy chứng tỏ rằng:
a) 1/41+1/42+1/43+...+1/79+1/80>7/12
b)11/15<1/21+1/22+1/23+...+1/59+1/60<3/2
Tính:1/41+1/42+1/43+.........+1/79+1/80
