A=-1/2*-2/3*-3/4*..*-2013/2014

A=-1*-2*-3*...*-2013/2*3*4*...*2014

A=-1/2014

ta có(-1)^2015=-1

B=-1/2015>-1/2014=A

nên A<B

Cẩm Nhung hả

Giup to!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!huhu

\(\left(2\frac{4}{5}.x+50\right):\frac{2}{3}=-51\)

\(\left(2\frac{4}{5}.x+50\right)\)      = (- 51) x \(\frac{2}{3}\)

\(\left(2\frac{4}{5}.x+50\right)\)      = - 34

\(2\frac{4}{5}.x\)                   = -34 - 50

\(2\frac{4}{5}.x\)                   = - 84

x                           = -84 : \(2\frac{4}{5}\)

x                           = -30

(14/5 . x + 50) : 2/3 = -51

(14/5 . x + 50) = -51 . 2/3

(14/5 . x + 50) = -34

14/5 . x = -34 - 50

14/5 . x = -84

x = -84 : 14/5

x = -30

2x-\(\frac{1}{3}\)=1-\(\frac{5}{6}\)
2x-\(\frac{1}{3}\)=\(\frac{1}{6}\)
2x=\(\frac{1}{6}\)+\(\frac{1}{3}\)
2x=1/6 +2/6
2x=\(\frac{1}{2}\)
x=1/2 : 2
x/\(\frac{1}{4}\)

\(\frac{7}{9}\):(2+\(\frac{3}{4}\)x)+\(\frac{5}{9}\)=\(\frac{23}{27}\)
7/9 :(2+3/4x)=\(\frac{23}{27}\)-\(\frac{5}{9}\)
7/9 :(2+3/4x)=\(\frac{23}{27}\)-\(\frac{15}{27}\)
7/9 :(2+3/4x)=\(\frac{8}{27}\)
(2+3/4x)      =\(\frac{7}{9}\) . \(\frac{27}{8}\)
(2+3/4x)   =\(\frac{21}{8}\)
\(\frac{3}{4}\)x            =\(\frac{21}{8}\)-2
3/4x          =21/8 -16/8
3/4x          = 5/8
    x           =\(\frac{5}{8}\) : \(\frac{3}{4}\)   
    x           =5/8 . 4/3
    x           =\(\frac{20}{24}\)
 

mk biet nhung dai dong lam

a) Ta có:

\(\dfrac{2929-101}{2.2929-404}=\dfrac{29.101-101}{2.29.101-4.101}=\dfrac{101.\left(29-1\right)}{101.\left(2.29-4\right)}=\dfrac{101.28}{101.54}=\dfrac{28}{54}=\dfrac{14}{27}\)

b) Ta có:

\(\dfrac{2.3+4.6+14.21}{3.5+6.10+21.35}=\dfrac{2.3+2.3.2^2+2.3.7^2}{3.5+3.5.2^2+3.5.7^2}=\dfrac{2.3.\left(1+2^2+7^2\right)}{3.5.\left(1+2^2+7^2\right)}=\dfrac{2.3}{3.5}=\dfrac{2}{5}\)

\(\frac{a+b+c}{2011+2012+2013}=\frac{a}{2011}+\frac{b}{2012}+\frac{c}{2013}\ge\frac{\left(\sqrt{a}+\sqrt{b}+\sqrt{c}\right)^2}{2011+2012+2013}=\frac{a+b+c+2\left(\sqrt{ab}+\sqrt{ac}+\sqrt{ac}\right)}{2011+2012+2013}\ge\frac{a+b+c}{2011+2012+2013}\)

=> a =b =c= 0

* 1/2 + x = 5/6  => x =5/6 - 1/2 = 2/6 = 1/3

*x + 1/4 =3/4  => x = 3/4 - 1/4 =2/4= 1/2

*5/6 - x = 1/3  => x = 5/6 -1/3 = 3/6 = 1/2 

*3/10 + x = 1/2  => x = 1/2 -3/10  = 2/10 = 1/5

sai

sai