So sánh \(2\cdot2016\)và \(2017^2-2016^2\)
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So sánh \(\sqrt{2017^2-1}-\sqrt{2016^2-1}\)và \(\frac{2\cdot2016}{\sqrt{2017^2-1}+\sqrt{2016^2-1}}\)
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Ta có :
\(\sqrt{2017^2-1}-\sqrt{2016^2-1}=\frac{2017^2-1-2016^2+1}{\sqrt{2017^2-1}+\sqrt{2016^2-1}}=\frac{2017+2016}{\sqrt{2017^2-1}+\sqrt{2016^2-1}}\)
\(>\frac{2016+2016}{\sqrt{2017^2-1}+\sqrt{2016^2-1}}=\frac{2.2016}{\sqrt{2017^2-1}+\sqrt{2016^2-1}}\)
Vậy \(\sqrt{2017^2-1}-\sqrt{2016^2-1}>\frac{2.2016}{\sqrt{2017^2-1}+\sqrt{2016^2-1}}\)
so sánh
\(\sqrt{2017^2-1}-\sqrt{2016^2-1}\)và \(\frac{2\cdot2016}{\sqrt{2017^2-1}+\sqrt{2016^2-1}}\)
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\(A=\sqrt{\left(2017-1\right)\left(2017+1\right)}-\sqrt{\left(2016-1\right)\left(2016+1\right)}\)
\(=\sqrt{2016.2018}-\sqrt{2015.2017}< \sqrt{2018.2018}-\sqrt{2015.2015}\)
\(=2018-2015=3\)
\(\Rightarrow\frac{1}{A}>\frac{1}{3}\)
\(B=\frac{2.2016}{A}>\frac{2.2016}{3}=1344>3>A\)
Vậy ta được B lớn hơn A rất nhiều :))
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a: Ta có: \(A=2018^2-2017^2=2018+2017\)
\(B=2017^2-2016^2=2017+2016\)
mà 2018>2016
nên A>B
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A = \(\frac{2015.2016-1}{2015.2016}\)= \(\frac{2015.2016}{2015.2016}\)\(-\)\(\frac{1}{2015.2016}\)= 1 \(-\)\(\frac{1}{2015.2016}\)
B = \(\frac{2016.2017-1}{2016.2017}\)= \(\frac{2016.2017}{2016.2017}\)\(-\)\(\frac{1}{2016.2017}\)= 1 \(-\)\(\frac{1}{2016.2017}\)
Vì \(\frac{1}{2015.2016}\)> \(\frac{1}{2016.2017}\)
=> 1 \(-\)\(\frac{1}{2015.2016}\)< \(1-\)\(\frac{1}{2016.2017}\)
=> A < B
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Ta có \(2017^2-2016^2=\left(2017-2016\right)\left(2017+2016\right)=2\cdot2016+1>2\cdot2016\)
Do đó \(2\cdot2016< 2017^2-2016^2\)