so sánh 2 số:
a, \(\sqrt{2014}+\sqrt{2016}\) và \(2\sqrt{2015}\)
b, \(\sqrt{2008}+\sqrt{2009}+\sqrt{2010}\) và \(\sqrt{2005}+\sqrt{2007}+\sqrt{2015}\)
so sánh\(\sqrt{2008}+\sqrt{2009}+\sqrt{2010}\)và\(\sqrt{2005}+\sqrt{2007}+\sqrt{2015}\)
So sánh: \(\sqrt{2008}+\sqrt{2009}+\sqrt{2010}\) và \(\sqrt{2005}+\sqrt{2007}+\sqrt{2015}\)
Ta có
\(\hept{\begin{cases}\sqrt{2008}+\sqrt{2005}< \sqrt{2015}+\sqrt{2009}\left(1\right)\\\sqrt{2010}+\sqrt{2007}< \sqrt{2015}+\sqrt{2009}\left(2\right)\end{cases}}\)
\(\Rightarrow\frac{1}{\sqrt{2008}+\sqrt{2005}}+\frac{1}{\sqrt{2010}+\sqrt{2007}}>\frac{2}{\sqrt{2015}+\sqrt{2009}}\)
\(\Leftrightarrow\frac{\sqrt{2008}-\sqrt{2005}}{3}+\frac{\sqrt{2010}-\sqrt{2007}}{3}>\frac{\sqrt{2015}-\sqrt{2009}}{3}\)
\(\Leftrightarrow\sqrt{2008}+\sqrt{2009}+\sqrt{2010}>\sqrt{2005}+\sqrt{2007}+\sqrt{2015}\)
A=√2008+√2009+√2010A=2008+2009+2010 và B=√2005+√2007+√2015
k và kb với mình nha !!!
so sánh \(\sqrt{2015}-\sqrt{2014}\) và \(\sqrt{2016}-\sqrt{2015}\)
Ta có: \(\sqrt{2015}-\sqrt{2014}=\dfrac{2015-2014}{\sqrt{2015}+\sqrt{2014}}>\dfrac{2016-2015}{\sqrt{2016}+\sqrt{2015}}=\sqrt{2016}-\sqrt{2015}\)
Ta có: √2015−√2014=2015−2014√2015+√2014>2016−2015√2016+√2015=√2016−√2015
So sánh A và B
\(A=\sqrt{2009}+\sqrt{2010}+\sqrt{2011}\)
\(B=\sqrt{2007}+\sqrt{2008}+\sqrt{2015}\)
\(A-B=\sqrt{2009}-\sqrt{2007}+\sqrt{2010}-\sqrt{2008}+\sqrt{2011}-\sqrt{2015}\)
\(=\frac{2}{\sqrt{2009}+\sqrt{2007}}+\frac{2}{\sqrt{2010}+\sqrt{2008}}-\frac{4}{\sqrt{2011}+\sqrt{2015}}\)
Ta có \(\left\{{}\begin{matrix}\sqrt{2009}+\sqrt{2007}< \sqrt{2011}+\sqrt{2015}\\\sqrt{2010}+\sqrt{2008}< \sqrt{2011}+\sqrt{2015}\end{matrix}\right.\)
\(\Rightarrow\frac{2}{\sqrt{2009}+\sqrt{2007}}+\frac{2}{\sqrt{2010}+\sqrt{2008}}>\frac{2}{\sqrt{2011}+\sqrt{2015}}+\frac{2}{\sqrt{2011}+\sqrt{2015}}=\frac{4}{\sqrt{2011}+\sqrt{2015}}\)
\(\Rightarrow\frac{2}{\sqrt{2009}+\sqrt{2007}}+\frac{2}{\sqrt{2010}+\sqrt{2008}}-\frac{4}{\sqrt{2011}+\sqrt{2015}}>0\)
\(\Rightarrow A-B>0\Rightarrow A>B\)
cho A=\(\sqrt{2009}+\sqrt{2010}+\sqrt{2011}\)
B=\(\sqrt{2007}+\sqrt{2008}+\sqrt{2015}\)
So sánh ; \(\sqrt{2016}-\sqrt{2015}và\sqrt{2015}-\sqrt{2014}\)
Áp dụng bđt \(\frac{\sqrt{a}+\sqrt{b}}{2}< \sqrt{\frac{a+b}{2}}\) với a > 0; b > 0; a \(\ne\) b ta có:
\(\frac{\sqrt{2016}+\sqrt{2014}}{2}< \sqrt{\frac{2016+2014}{2}}\)
\(\Rightarrow\frac{\sqrt{2016}+\sqrt{2014}}{2}< \sqrt{\frac{4030}{2}}\)
\(\Rightarrow\frac{\sqrt{2016}+\sqrt{2014}}{2}< \sqrt{2015}\)
\(\Rightarrow\sqrt{2016}+\sqrt{2014}< 2.\sqrt{2015}\)
\(\Rightarrow\sqrt{2016}-\sqrt{2015}< \sqrt{2015}-\sqrt{2014}\)
So sánh
a/ \(\sqrt{2010} -\sqrt{2009} và \sqrt{2008} - \sqrt{2007}\)
a/Tính: A= \(\sqrt{1+2006^2+\frac{2006^2}{2007^2}}+\frac{2006}{2007}\)
b/Cho A=\(\sqrt{2015^2-1}-\sqrt{2014^2-1}\)và B=\(\frac{2.2014}{\sqrt{2015^2-1}+\sqrt{2014^2-1}}\)
So sánh A vs B
So sánh : \(\sqrt{2016}-\sqrt{2015}và\sqrt{2015}-\sqrt{2014}\)
Ko dùng máy tính
\(\sqrt{2016}-\sqrt{2015}=\dfrac{1}{\sqrt{2016}+\sqrt{2015}}\)
\(\sqrt{2015}-\sqrt{2014}=\dfrac{1}{\sqrt{2015}+\sqrt{2014}}\)
mà \(\sqrt{2016}+\sqrt{2015}>\sqrt{2014}+\sqrt{2015}\)
nên \(\sqrt{2016}-\sqrt{2015}< \sqrt{2015}-\sqrt{2014}\)