\(A=\dfrac{-9}{10^{2010}}+\dfrac{-19}{10^{2011}}=\dfrac{-90}{10^{2011}}+\dfrac{-19}{10^{2011}}=\dfrac{-109}{10^{2011}}\)

\(B=\dfrac{-9}{10^{2011}}+\dfrac{-19}{10^{2010}}=\dfrac{-9}{10^{2011}}+\dfrac{-190}{10^{2011}}=\dfrac{-199}{10^{2011}}\)

Mà \(\dfrac{-109}{10^{2011}}>\dfrac{-199}{10^{2011}}\)

\(\Rightarrow A>B\).

tao chịu ,

chắc mày bít t là ai

`(12/999 +23/200 -34/201 ) .(1/2-1/3-1/6)`

`= (12/999 +23/200 -34/201 ) .( 3/6 - 2/6-1/6)`

` =(12/999 +23/200 -34/201 ) . 0/6`

` =(12/999 +23/200 -34/201 ) . 0`

`=0`

   ( - \(\dfrac{2}{3}\) + 1\(\dfrac{1}{4}\) - \(\dfrac{1}{6}\)) - \(\dfrac{24}{10}\)

= - \(\dfrac{2}{3}\)  + \(\dfrac{5}{4}\)  - \(\dfrac{1}{6}\) - \(\dfrac{24}{10}\)

= \(\dfrac{-40}{60}\) + \(\dfrac{25}{60}\) - \(\dfrac{10}{60}\) - \(\dfrac{144}{60}\)

= \(-\dfrac{169}{60}\)

`1/5 + 1/6 -1/10 +1/12 + 1/7 -1/14`

`= (1/5-1/10)+(1/6+1/12)+(1/7-1/14)`

`= (2/10-1/10) +(2/12+1/12) +(2/14-1/14)`

`= 1/10 + 1/4 + 1/14`

`= 4/40 + 10/40 +1/14`

`= 14/40 + 1/14`

`=7/20 +1/14`

`=59/140`

\(B=\dfrac{1}{5}+\dfrac{1}{6}-\dfrac{1}{10}+\dfrac{1}{12}+\dfrac{1}{7}-\dfrac{1}{14}\)

\(B=\left(\dfrac{1}{5}-\dfrac{1}{10}\right)+\left(\dfrac{1}{6}+\dfrac{1}{12}\right)+\left(\dfrac{1}{7}-\dfrac{1}{14}\right)\)

\(B=\left(\dfrac{2}{10}-\dfrac{1}{10}\right)+\left(\dfrac{2}{12}+\dfrac{1}{12}\right)+\left(\dfrac{2}{14}-\dfrac{1}{14}\right)\)

\(B=\dfrac{1}{10}+\dfrac{1}{4}+\dfrac{1}{14}\)

\(B=\dfrac{14}{140}+\dfrac{35}{140}+\dfrac{10}{140}\)

\(B=\dfrac{59}{140}\)

Câu `a` chỗ `3'7` là `3/7` nhỉ?

`a)5/11 . 6/11:3/7`

`=30/121 . 7/3`

`=70/121`

`b)5/2+13/4:2-17/4`

`=5/2+13/8-17/4`

`=33/8-17/4`

`=-1/8`

`a, 5/11 . 6/11 : 3/7`

`= 5/11 . 6/11 . 7/3`

`=(5.6.7)/(11.11.3)`

`= 210/363`

`=70/121`

`b, 5/2 + 13/4 : 2 -17/4`

`=  5/2 + 13/4 . 1/2-17/4`

`=5/2 +13/8-17/4`

`=20/8+13/8-17/4`

`= 33/8 -17/4`

`=33/8 - 34/8`

`=-1/8`

`8/15-x:3/4=11/18`

`x:3/4=8/15-11/18`

`x:3/4=-7/90`

`x=-7/90 . 3/4`

`x=-7/120`

\(\dfrac{8}{15}-x:\dfrac{3}{4}=\dfrac{11}{18}\)

          \(x:\dfrac{3}{4}=\dfrac{8}{15}-\dfrac{11}{18}\)   

          \(x:\dfrac{3}{4}=-\dfrac{7}{90}\)

          \(x=-\dfrac{7}{90}.\dfrac{3}{4}\)

          \(x=-\dfrac{7}{120}\)

       Vậy \(x=-\dfrac{7}{120}\)

\(\left(x-3\right)^{2x}:\left(x-3\right)^x=1\)

\(\Rightarrow\left(x-3\right)^{2^x}:\left(x-3\right)^x=1\)

\(\Rightarrow\left(x-3\right)^2:\left(x-3\right)^x=1\)

Mà kết quả ở đây bằng 1 nên chỉ có 1 phép chia duy nhất là \(1:1=1\)

Vậy \(\left(x-3\right)^2=\left(x-3\right)^x=1;\)

\(\Rightarrow\left(x-3\right)=\left(x-3\right)=1\) vì chỉ có lũy thừa của 1 mới bằng 1.

\(\Rightarrow x=3+1=4\)

cảm ơn ạ

\(A=\dfrac{10^{11}+1}{10^{12}-1}\)

\(\Rightarrow10A=\dfrac{10^{11}+1}{10^{12}-1}.10\)

\(\Rightarrow10A=\dfrac{10\left(10^{11}+1\right)}{10^{12}-1}\)

\(\Rightarrow10A=\dfrac{10^{12}-10}{10^{12}-1}\)

\(B=\dfrac{10^{10}+1}{10^{11}+1}\)

\(\Rightarrow10B=\dfrac{10^{10}+1}{10^{11}+1}.10\)

\(\Rightarrow10B=\dfrac{\left(10^{10}+1\right).10}{10^{11}+1}\)

\(\Rightarrow10B=\dfrac{10^{11}+10}{10^{11}+1}\)

Ta thấy:

 \(10^{12}-1>10^{12}-10>0\Rightarrow10A< 1\)

\(0< 10^{11}+1< 10^{11}+10\Rightarrow10B>1\)

Mà \(10A< 1;10B>1\)

\(\Rightarrow B>A\).

\(a.\dfrac{7}{8}+\dfrac{1}{2}\text{=}\dfrac{11}{8}\)

\(b.\dfrac{5}{6}+\left(-2\right)\text{=}\dfrac{-7}{6}\)

\(c.\dfrac{2}{5}+\dfrac{-3}{8}\text{=}\dfrac{1}{40}\)

\(d.\dfrac{5}{7}-\dfrac{3}{8}\text{=}\dfrac{19}{56}\)

\(e.\dfrac{3}{4}-\dfrac{1}{2}+\dfrac{7}{6}\text{=}\dfrac{17}{12}\)

`a. 7/8 + 1/2 = 7/8 + 4/8=(7+4)/8=11/8`

`b. 5/6 + (-2) =5/6 + (-12/6)=-7/6`

`c. 2/5 + -3/8   = 16/40 + (-15/40)=1/40`

`d. 5/7  - 3/8  = 40/56 - 21/56=19/56`

`e. 3/4 - 1/2 +7/6= 3/4 - 2/4 + 7/6= 1/4 + 7/6= 6/24 + 28/24= 34/24=17/12`