1. CMR:1/1.2+1/3.4+1/5.6+....+1/49.50=1/26+1/27+.......+1/50
2.A=1/1.2+1/2.3+.....+1/99.100.CMR:7/12<A<5/6
3.tim x
a.x+1/10+ x+1/12 +x+1/14 + x+1/16 + x+1/18 + x+1/20
b.x+1/2000 + x+2/1999 =x+3/1998 + x+4/1977
giup minh nha cac ban
Thực hiện phép tình
\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}\)
1) chứng minh : \(\frac{1}{1.2}+\frac{1}{3.4}+...+\frac{1}{49.50}=\frac{1}{26}+\frac{1}{27}+...+\frac{1}{50}\)
2) cho :\(A=\frac{1}{1.2}+\frac{1}{3.4}+...+\frac{1}{99.100}\)Chứng minh \(\frac{7}{12}< A< \frac{5}{6}\)
Tính:
a) C=\(\frac{8^{10}+4^{10}}{8^4+4^{11}}\)
b) D=\(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{2015.2016}\)
c) E=\(\frac{1}{3}-\frac{3}{4}+\frac{3}{5}+\frac{2}{1015}-\frac{1}{36}+\frac{1}{15}-\frac{2}{9}\)
A=1+1/1.2+1+1/1.2.3+.......+1/1.2.3.n < 1+1/1.2+1/2.3+.......+1/k(k+1)
Tính :
a. T = \(\dfrac{1}{1.2}+\dfrac{1}{2.3}+....+\dfrac{1}{99.100}\)
b. H = \(\left(1-\dfrac{1}{2}\right).\left(1-\dfrac{1}{3}\right)......\left(1-\dfrac{1}{n+1}\right)\) với n e N
c. B = \(-66.\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{11}\right)+124.\left(-37\right)+63.\left(-124\right)\)
Giúp mik nha đề hsg Toán hơi khó
Tính A = 1.2 + 2.3 + 3.4 + … + n.(n + 1)
tính:
(1-1/1.2)+(1-1/2.3)+...+(1-1/1994.1995)+(1-1/1995.1996)
Tính giá trị biểu thức sau:
1.\(B=\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)......\left(1-\dfrac{1}{n+1}\right)\)với n thuộc N
2.\(A=\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{99.100}\)
3.\(C=-66.\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{11}\right)+124.\left(-37\right)+63.\left(-124\right)\)
4.\(D=\dfrac{7}{4}\left(\dfrac{33}{12}\dfrac{3333}{2020}\dfrac{333333}{303030}\dfrac{33333333}{42424242}\right)\)
giúp mik nhé