\(A=\frac{1}{2.3}+\frac{1}{3.4}+.....+\frac{1}{49.50}\)
\(A=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)
\(A=\frac{1}{1}-\frac{1}{50}\)
\(A=\frac{49}{50}\)
Vì \(\frac{245}{420}< \frac{245}{294}< \frac{245}{250}\)
Vậy \(\frac{7}{12}< \frac{49}{50}< \frac{5}{6}\)
Cho :A=1/1.2 +1/2.3 + 1/3.4 + .......+1/49+50. Chứng minh rằng 7/12 < A < 5/6.
Chứng minh rằng 1/1.2 + 1/2.3 + 1/3.4 +........+1/49+50 = 1/26 + 1/27 +1/28 +.....+ 1/50
1.Chứng minh rằng:
a) \(\dfrac{1}{1.2}+\dfrac{1}{3.4}+\dfrac{1}{5.6}+...+\dfrac{1}{49.50}=\dfrac{1}{26}+\dfrac{1}{27}+...+\dfrac{1}{50}\)
b) Cho A = \(\dfrac{1}{1.2}+\dfrac{1}{3.4}+\dfrac{1}{5.6}+...+\dfrac{1}{99.100}\)
Chứng minh \(\dfrac{7}{12}< A< \dfrac{5}{6}\)
2. Tìm a, b \(\in\) Q, biết
a - b = a.b = a : b
9 Cho A= \(\dfrac{1}{1.2}+\dfrac{1}{3.4}+\dfrac{1}{5.6}+...+\dfrac{1}{99.100}.\) Chứng minh rằng : \(\dfrac{7}{12}< A< \dfrac{5}{6}\)
Cho \(A=\frac{1}{1.2}+\frac{1}{3.4}+\frac{1}{5.6}+...+\frac{1}{49.50}=\frac{1}{26}+\frac{1}{27}+\frac{1}{28}+...+\frac{1}{50}\)
Chứng minh rằng: \(\frac{7}{12}< A< \frac{5}{6}\)
Các bạn giúp mk với mk cần gấp thank you!!!
Cho A=1/1.2+1/3.4+1/5.6+...+1/99.100,CMR:7/12<A<5/6
1.Tìm số hữu tỉ x:
a)\(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)
b)\(\frac{x+4}{2000}+\frac{x+3}{2001}=\frac{x+2}{2002}+\frac{x+1}{2003}\)
2.CMR:
a)\(\frac{1}{1.2}+\frac{1}{3.4}+\frac{1}{5.6}+...+\frac{1}{49.50}=\frac{1}{26}+\frac{1}{27}+\frac{1}{28}+...+\frac{1}{50}\)
b)Cho \(A=\frac{1}{1.2}+\frac{1}{3.4}+\frac{1}{5.6}+...+\frac{1}{99.100}\)
Chứng minh rằng : \(\frac{7}{12}< A< \frac{5}{6}\)
Cho A = 1/1.2 + 1/3.4 + 1/5.6 +...+ 1/49.50
B = 1/1 + 1/2 + 1/3 + 1/4 + ... + 1/49 + 1/50
C = 1/2 + 1/4 + 1/6 +...+1/48 + 1/50
CMR : A = B - 2C
Cho \(A=\frac{1}{1.2}+\frac{1}{3.4}+\frac{1}{5.6}+......+\frac{1}{99.100}\)
Chứng minh rằng \(\frac{7}{12}< A< \frac{5}{6}\)