\(A=\dfrac{x^2-2x+2007}{x^2}\)
\(\Rightarrow\dfrac{2007}{2006}A=\dfrac{2006x^2+x^2-2\times x\times2007+2007^2}{2006x^2}\)
\(=1+\dfrac{\left(x-2007\right)^2}{2016x^2}\ge1\)
\(\Rightarrow A\ge\dfrac{2006}{2007}\)
Dấu "=" xảy ra khi x - 2007 = 0
⇔ x = 2007
Vậy Min A = \(\dfrac{2006}{2007}\Leftrightarrow x=2007\)
\(A=\dfrac{x^2-2x+2007}{x^2}\)
\(A=\dfrac{2007x^2-2.2007x+2007^2}{2007^2.x^2}\)
\(A=\dfrac{\left(x-2007\right)^2}{2007^2.x^2}+\dfrac{2006}{2007^2}\ge\dfrac{2006}{2007^2}\)
Dấu = xảy ra khi: ( x- 2007)2 =0
=> x = 2007
Vậy GTNN của A là \(\dfrac{2006}{2007^2}\) khi x = 2007
\(A=\dfrac{x^2-2x+2017}{x^2}\)
\(\Rightarrow\dfrac{2017}{2016}A=\dfrac{2017x^2-2\times2017\times x+2017^2}{2016x^2}\)
\(=\dfrac{\left(x-2017\right)^2}{2016x^2}+1\ge1\)
\(\Rightarrow A\ge\dfrac{2006}{2007}\)
Dấu "=" xảy ra khi x - 2017 = 0
⇔ x = 2017
Vậy Min A = \(\dfrac{2006}{2007}\) ⇔ x = 2017