\(10\cdot\dfrac{10^3+5}{10^4+5}=\dfrac{10^4+5+45}{10^4+5}=1+\dfrac{45}{10^4+5}\)
\(10\cdot\dfrac{10^2+5}{10^3+5}=\dfrac{10^3+5+45}{10^3+5}=1+\dfrac{45}{10^3+5}\)
mà \(\dfrac{45}{10^4+5}< \dfrac{45}{10^3+5}\)
nên \(\dfrac{10^3+5}{10^4+5}< \dfrac{10^2+5}{10^3+5}\)