HOC24
Lớp học
Môn học
Chủ đề / Chương
Bài học
Ta có : \(6.2^{12}+2^{13}=3.2.2^{12}+2^{13}=3.2^{13}+2^{13}=2^{13}\left(3+1\right)=2^{13}.4=2^{13}.2^2=2^{15}=\left(2^3\right)^5=8^5\)\(3^{10}=\left(3^2\right)^5=9^5\)
Vì 8 < 9
=> 85 < 95 ( vì 5 > 0 )
=> 6.212 + 213 < 310
Vậy 6.212 + 213 < 310
a, 22x+1 = 83.165
=> 22x+1 = (23)3 . (24)5
=> 22x+1 = 29 . 220
=> 22x+1 = 229
=> 2x+1 = 29 ( vì cơ số 2 > 0 )
=> 2x = 29 - 1
=> 2x = 28
=> x = 28 : 2
=> x = 14
Vậy x = 14
Ta có : \(\dfrac{1}{1.4}+\dfrac{1}{4.7}+\dfrac{1}{7.10}+...+\dfrac{1}{97.100}\)
= 3( \(\dfrac{1}{1.4}+\dfrac{1}{4.7}+\dfrac{1}{7.10}+...+\dfrac{1}{97.100}\) ).\(\dfrac{1}{3}\)
= (\(\dfrac{3}{1.4}+\dfrac{3}{4.7}+\dfrac{3}{7.10}+...+\dfrac{3}{97.100}\)).\(\dfrac{1}{3}\)
= \(\left(\dfrac{4-1}{1.4}+\dfrac{7-4}{4.7}+\dfrac{10-7}{7.10}+...+\dfrac{100-97}{97.100}\right).\dfrac{1}{3}\) = \(\left(\dfrac{4}{1.4}-\dfrac{1}{1.4}+\dfrac{7}{4.7}-\dfrac{4}{4.7}+\dfrac{10}{7.10}-\dfrac{7}{7.10}+...+\dfrac{100}{97.100}-\dfrac{97}{97.100}\right).\dfrac{1}{3}\) = \(\left(1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{97}-\dfrac{1}{100}\right).\dfrac{1}{3}\) =\(\left(1-\dfrac{1}{100}\right).\dfrac{1}{3}\)
= \(\dfrac{99}{100}.\dfrac{1}{3}\)
= \(\dfrac{99}{100.3}\)
= \(\dfrac{33}{100}\)
Là số 19
Ta có : B = \(\dfrac{2012+2013}{2013+2014}=\dfrac{2012}{2013+2014}+\dfrac{2013}{2013+2014}\) Ta có :
\(\dfrac{2012}{2013}>\dfrac{2012}{2013+2014}\)( vì 2012 > 0; 0<2013<2013+2014 )
\(\dfrac{2013}{2014}>\dfrac{2013}{2013+2014}\)( vì 2013>0; 0<2014<2013+2014 )
=> \(\dfrac{2012}{2013}+\dfrac{2013}{2014}>\dfrac{2012}{2013+2014}+\dfrac{2013}{2013+2014}\) => A > B
Vậy A > B
10.3546.345.11=134570700
Ta có : A =\(\dfrac{54.107-53}{53.107+54}=\dfrac{53.107+107-53}{53.107+54}=\dfrac{53.107+\left(107-53\right)}{53.107+54}=\dfrac{53.107+54}{53.107+54}=1\)Ta có : B = \(\dfrac{135.269-133}{134.269+135}=\dfrac{134.269+269-133}{134.269+135}=\dfrac{134.269+\left(269-133\right)}{134.269+135}=\dfrac{134.269+136}{134.269+135}=\dfrac{134.269+135}{134.269+135}+\dfrac{1}{134.269+135}=1+\dfrac{1}{134.269+135}\) => B > 1 ( vì \(\dfrac{1}{134.269+135}>0\) )
Mà A = 1
=> A < B
Vậy A < B