A=1/2x(1/2+1/6+1/12+...+1/10100)
=1/2x(1/1x2+1/2x3+1/3x4+...+1/100x101)
=1/2x(1-1/2+1/2-1/3+1/3+1/4+...+1/100-1/101)
=1/2x(1-1/101)
=1/2x100/101=50/101 (đúng thì cho mk nhoa)
a) A = 1/1.2+ 1/3.4+ 1/5.6+...+ 1/99.100
CMR: 7/12<A< 5/6
b) CMR: 1/1.2+ 1/3.4+ 1/5.6+...+1/49.50 = 1/26+ 1/27+ 1/28+...+1/50
cmr A=1/1.2+1/3.4+1/5.6+.......+1/49.50=1/26+1/27+........+1/50
1, CMR: \(\frac{7}{12}<\frac{1}{1.2}+\frac{1}{3.4}+\frac{1}{5.6}+...+\frac{1}{97.98}+\frac{1}{99.100}<\frac{5}{6}\)
2, CMR: \(\frac{1}{1.2}+\frac{1}{3.4}+\frac{1}{5.6}+...+\frac{1}{47.48}+\frac{1}{49.50}=\frac{1}{26}+\frac{1}{27}+\frac{1}{28}+...+\frac{1}{49}+\frac{1}{50}\)
CMR: 1/1.2+1/3.4+1/5.6+....+1/49.50+1/26=1/27=....=1/50
1, CMR: \(\frac{7}{12}<\frac{1}{1.2}+\frac{1}{3.4}+\frac{1}{5.6}+...+\frac{1}{97.98}+\frac{1}{99.100}<\frac{5}{6}\)
2, CMR: \(\frac{1}{1.2}+\frac{1}{3.4}+\frac{1}{5.6}+...+\frac{1}{47.48}+\frac{1}{49.50}=\frac{1}{26}+\frac{1}{27}+\frac{1}{28}+...+\frac{1}{49}+\frac{1}{50}\)
cmr :
1/1.2 + 1/3.4+1/5.6+...+1/49.50 = 1/26+1/27+1/28+...+1/50
Bài 1 Tính giá trị biểu thức :
A = 3/1.4 + 5/4.9 + 7/9.16 + 9/16.25 + 11/25.36
B = 3/1.4 + 3/4.7 + ... + 3/100.103
C = 3/1.4 + 6/4.10 + 9/10.19 + 12/19.31 + 15/31.46 + 18/46.64
Bài 2 Chứng minh rằng :
1/1.2 + 1/3.4 + 1/5.6 + ... + 1/49.50 = 1/26 + 1/27 + 1/28 + ... + 1/50
1. Cho A = 1/(1.2)+1/(3.4)+...+1/(99.100).
Chứng minh 7/12 < A <5/6
2.Chứng minh:
1/(1.2)+1/(3.4)+...+1/(49.50)=1/26+1/27+...+1/50
Chứng minh 1/1.2 + 1/3.4 +1/5.6 +...... + 1/49.50 =1/26 + 1/27 + ... +1/50
