Tính nhẩm :

  1. ( 1999 + 313 ) – 1999 ; ( 1435 + 213 ) -13
  2. K
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    Giải :

    1. ( 1999 + 313 ) – 1999 = 1999 – 1999 + 313 = 313

    ( 1435 + 213 ) – 13 = 1435 + ( 213 – 13 ) = 1435 + 200 = 1635

    1. 2034 – ( 34 + 1560 ) = ( 2034 – 34 ) – 1560 = 2000 – 1560 = 440

    1972 – ( 364 + 972 ) = 1972 – 972 – 368 = 1000 – 368 = 632

          c.    364 – ( 364 – 111 ) = 364 – 364 + 111 = 111

                 249 – ( 75-51 ) = ( 249 + 51 ) – 75 = 300 – 75 = 225

    31 tháng 1 2016

    1.= 574.499+3

    =(574)499.573

    = .....1499.B3

    A1.B3

    =......3

    Cau kia van dung ma lam

    31 tháng 1 2016

    1 chữ số tận cùng là 3

    2 chữ số tận cùng là 7

    16 tháng 9 2017

     Giúp mình với :v

    16 tháng 9 2017

    tự đi mà làm

    13 tháng 6 2017

    a, ( 1999 + 313 ) - 1999

    = 1999 - 1999 + 313

    = 313

    b, 364 - ( 364 - 111 )

    = 364 - 364 - 111

    = -111

    c, 249 - ( 75- 51 )

    = 249 - 24

    = 225

    13 tháng 6 2017

    a) ( 1999 + 313 ) - 1999

    = 1999 + 313 - 1999

    = ( 1999 - 1999 ) + 313

    = 0 + 313

    b) 364 - ( 364 - 111 )

    = 364 - 364 + 111

    = 0 + 111

    = 111

    c) 249 - 75 + 51

    = 174 + 51 

    = 225

    9 tháng 5 2019

    giúp mik nha chiều này 6:00 mik nộp rồi

    ai nhanh mik sẽ k cho 3 k

    \(2\frac{3}{5}x-\frac{1}{7}=1\frac{9}{35}\)

    \(\frac{13}{5}x=\frac{44}{35}+\frac{1}{7}\)

    \(\frac{13}{5}x=\frac{7}{5}\)

    \(x=\frac{7}{5}:\frac{13}{5}\\ x=\frac{7}{13}\)

    22 tháng 8 2020

    1) Ta có : \(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)

    \(\Rightarrow\left(x+1\right)\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\right)=0\)

    Vì \(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\ne0\)

    => x + 1 = 0

    => x = - 1

    b) \(\frac{x+4}{2006}+\frac{x+3}{2007}=\frac{x+2}{2008}+\frac{x+1}{2009}\)

    => \(\left(\frac{x+4}{2006}+1\right)+\left(\frac{x+3}{2007}+1\right)=\left(\frac{x+2}{2008}+1\right)+\left(\frac{x+1}{2009}+1\right)\)

    => \(\frac{x+2010}{2006}+\frac{x+2010}{2007}=\frac{x+2010}{2008}+\frac{x+2010}{2009}\)

    => \(\left(x+2010\right)\left(\frac{1}{2006}+\frac{1}{2007}-\frac{1}{2008}-\frac{1}{2009}\right)=0\)

    Vì \(\frac{1}{2006}+\frac{1}{2007}-\frac{1}{2008}-\frac{1}{2009}\ne0\)

    => x + 2010 = 0

    => x = -2010

    c) \(\frac{x+1945}{45}+\frac{x+1954}{54}=\frac{x+1975}{75}+\frac{x+1969}{69}\)

    \(\Rightarrow\left(\frac{x+1945}{45}-1\right)+\left(\frac{x+1954}{54}-1\right)=\left(\frac{x+1975}{75}-1\right)+\left(\frac{x+1969}{69}-1\right)\)

    => \(\frac{x+1900}{45}+\frac{x+1900}{54}=\frac{x+1900}{75}+\frac{x+1900}{69}\)

    => \(\left(x+1900\right)\left(\frac{1}{45}+\frac{1}{54}-\frac{1}{75}-\frac{1}{69}\right)=0\)

    => \(x+1900=0\left(\text{Vì }\frac{1}{45}+\frac{1}{54}-\frac{1}{75}-\frac{1}{69}\ne0\right)\)

    => x = -1900

    d) \(\frac{x+2008}{10}+\frac{x+2010}{9}=\frac{x+2012}{8}+\frac{x+2014}{7}\)

    => \(\left(\frac{x+2008}{10}+2\right)+\left(\frac{x+2010}{9}+2\right)=\left(\frac{x+2012}{8}+2\right)+\left(\frac{x+2014}{7}+2\right)\)

    => \(\frac{x+2028}{10}+\frac{x+2028}{9}=\frac{x+2028}{8}+\frac{x+2028}{7}\)

    => \(\left(x+2028\right)\left(\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}\right)=0\)

    => x + 2028 = 0 \(\left(\text{Vì }\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}\ne0\right)\)

    => x = -2028

    22 tháng 8 2020

    1) Ta có: \(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)

            \(\Leftrightarrow\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}-\frac{x+1}{13}-\frac{x+1}{14}=0\)

            \(\Leftrightarrow\left(x+1\right).\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\right)=0\)

      + TH1\(x+1=0\)\(\Leftrightarrow\)\(x=-1\)

      + TH2\(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}=0\)

          Vì \(\hept{\begin{cases}\frac{1}{10}>\frac{1}{13}\\\frac{1}{11}>\frac{1}{14}\\\frac{1}{12}>0\end{cases}}\)\(\Rightarrow\)\(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}>\frac{1}{13}+\frac{1}{14}\)

                \(\Rightarrow\)\(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}>0\)

                 mà \(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}=0\)

                 \(\Rightarrow\)Phương trình trên vô nghiệm

    Vậy \(x=-1\)

    2) Ta có: \(\frac{x+4}{2006}+\frac{x+3}{2007}=\frac{x+2}{2008}+\frac{x+1}{2009}\)

            \(\Leftrightarrow\left(\frac{x+4}{2006}+1\right)+\left(\frac{x+3}{2007}+1\right)-\left(\frac{x+2}{2008}+1\right)-\left(\frac{x+1}{2009}+1\right)=0\)

            \(\Leftrightarrow\frac{x+2010}{2006}+\frac{x+2010}{2007}-\frac{x+2010}{2008}-\frac{x+2010}{2009}=0\)

            \(\Leftrightarrow\left(x+2010\right).\left(\frac{1}{2006}+\frac{1}{2007}-\frac{1}{2008}-\frac{1}{2009}\right)=0\)

      + TH1\(x+2010=0\)\(\Leftrightarrow\)\(x=-2010\)

      + TH2\(\frac{1}{2006}+\frac{1}{2007}-\frac{1}{2008}-\frac{1}{2009}=0\)

          Vì \(\hept{\begin{cases}\frac{1}{2006}>\frac{1}{2008}\\\frac{1}{2007}>\frac{1}{2009}\end{cases}}\)\(\Rightarrow\)\(\frac{1}{2006}+\frac{1}{2007}>\frac{1}{2008}+\frac{1}{2009}\)

                  \(\Rightarrow\)\(\frac{1}{2006}+\frac{1}{2007}-\frac{1}{2008}-\frac{1}{2009}>0\)

                   mà \(\frac{1}{2006}+\frac{1}{2007}-\frac{1}{2008}-\frac{1}{2009}=0\)

                   \(\Rightarrow\)Phương trình trên vô nghiệm

    Vậy \(x=-2010\)

    3) Ta có: \(\frac{x+1945}{45}+\frac{x+1954}{54}=\frac{x+1975}{75}+\frac{x+1969}{69}\)

            \(\Leftrightarrow\left(\frac{x+1945}{45}-1\right)+\left(\frac{x+1954}{54}-1\right)-\left(\frac{x+1975}{75}-1\right)-\left(\frac{x+1969}{69}-1\right)=0\)

            \(\Leftrightarrow\frac{x+1900}{45}+\frac{x+1900}{54}-\frac{x+1900}{75}-\frac{x+1900}{69}=0\)

           \(\Leftrightarrow\left(x+1900\right).\left(\frac{1}{45}+\frac{1}{54}-\frac{1}{75}-\frac{1}{69}\right)=0\)

      

      + TH1\(x+1900=0\)\(\Leftrightarrow\)\(x=-1900\)

      + TH2\(\frac{1}{45}+\frac{1}{54}-\frac{1}{75}-\frac{1}{69}=0\)

          Vì \(\hept{\begin{cases}\frac{1}{45}>\frac{1}{75}\\\frac{1}{54}>\frac{1}{69}\end{cases}}\)\(\Rightarrow\)\(\frac{1}{45}+\frac{1}{54}>\frac{1}{75}+\frac{1}{69}\)

                  \(\Rightarrow\)\(\frac{1}{45}+\frac{1}{54}-\frac{1}{75}-\frac{1}{69}>0\)

                   mà \(\frac{1}{45}+\frac{1}{54}-\frac{1}{75}-\frac{1}{69}=0\)

                   \(\Rightarrow\)Phương trình trên vô nghiệm

    Vậy \(x=-1900\)

    4) Ta có: \(\frac{x-99}{5}+\frac{x-97}{7}=\frac{x-95}{9}+\frac{x-93}{11}\)

             \(\Leftrightarrow\left(\frac{x-99}{5}-1\right)+\left(\frac{x-97}{7}-1\right)-\left(\frac{x-95}{9}-1\right)-\left(\frac{x-93}{11}-1\right)=0\)

             \(\Leftrightarrow\frac{x-104}{5}+\frac{x-104}{7}-\frac{x-104}{9}-\frac{x-104}{11}=0\)

             \(\Leftrightarrow\left(x-104\right).\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{9}-\frac{1}{11}\right)=0\)

      

      + TH1\(x-104=0\)\(\Leftrightarrow\)\(x=104\)

      + TH2\(\frac{1}{5}+\frac{1}{7}-\frac{1}{9}-\frac{1}{11}=0\)

          Vì \(\hept{\begin{cases}\frac{1}{5}>\frac{1}{7}\\\frac{1}{9}>\frac{1}{11}\end{cases}}\)\(\Rightarrow\)\(\frac{1}{5}+\frac{1}{7}>\frac{1}{9}+\frac{1}{11}\)

                  \(\Rightarrow\)\(\frac{1}{5}+\frac{1}{7}-\frac{1}{9}-\frac{1}{11}>0\)

                   mà \(\frac{1}{5}+\frac{1}{7}-\frac{1}{9}-\frac{1}{11}=0\)

                   \(\Rightarrow\)Phương trình trên vô nghiệm

    Vậy \(x=104\)

    5) Ta có: \(\frac{x+2008}{10}+\frac{x+2010}{9}=\frac{x+2012}{8}+\frac{x+2014}{7}\)

            \(\Leftrightarrow\left(\frac{x+2008}{10}+2\right)+\left(\frac{x+2010}{9}+2\right)-\left(\frac{x+2012}{8}+2\right)-\left(\frac{x+2014}{7}+2\right)=0\)

            \(\Leftrightarrow\frac{x+2028}{10}+\frac{x+2028}{9}-\frac{x+2028}{8}-\frac{x+2028}{7}=0\)

            \(\Leftrightarrow\left(x+2028\right).\left(\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}\right)=0\)

        + TH1\(x+2028=0\)\(\Leftrightarrow\)\(x=-2028\)

        + TH2\(\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}=0\)

          Vì \(\hept{\begin{cases}\frac{1}{10}< \frac{1}{8}\\\frac{1}{9}< \frac{1}{7}\end{cases}}\)\(\Rightarrow\)\(\frac{1}{10}+\frac{1}{9}< \frac{1}{8}+\frac{1}{7}\)

                  \(\Rightarrow\)\(\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}< 0\)

                   mà \(\frac{1}{10}+\frac{1}{9}-\frac{1}{8}-\frac{1}{7}=0\)

                   \(\Rightarrow\)Phương trình trên vô nghiệm

    Vậy \(x=-2028\)

    Chúc bn hok tốt nha

    26 tháng 7 2020

    1. \(\frac{8^{10}}{4^{14}}=\frac{\left(2^3\right)^{10}}{\left(2^2\right)^{14}}=\frac{2^{30}}{2^{28}}=2^2=4\)

    2. \(\frac{6^5.5^3}{10^3}=\frac{6^5}{2^3}=\frac{6^3.6^2}{2^3}=3^3.6^2=27.36=972\)

    26 tháng 7 2020

    1) \(\frac{8^{10}}{4^{14}}=\frac{\left(2^3\right)^{10}}{\left(2^2\right)^{14}}=\frac{2^{30}}{2^{28}}=2^2=4\)

    2) \(\frac{6^5.5^3}{10^3}=\frac{2^5.3^5.5^3}{2^3.5^3}=2^2.3^5=972\)

    Học tốt!!!!

    15 tháng 7 2017

    100.2.5.10 = 10.10.10.10 = 104
    A = 103103 = 7.11.13.103
    B = 102.102 = 22.32.17
    C = 102.10.10102.10.10 = 22.3.17.103.5051
    D = 104104 = 23.7.11.132

    22 tháng 8 2020

    đọc cách lm trrong sbt nha bạn lớp 8

    22 tháng 8 2020

    mk học lớp 6 lên 7