Question

Answer 1

CHÚC EM HỌC TỐT

Answer 2

\(D=\dfrac{2x+1}{x^2+2}=\dfrac{4x+2}{2\left(x^2+2\right)}=\dfrac{x^2+4x+4-\left(x^2+2\right)}{2\left(x^2+2\right)}=\dfrac{\left(x+2\right)^2}{2\left(x^2+2\right)}-\dfrac{1}{2}\ge-\dfrac{1}{2}\)

\(D_{min}=-\dfrac{1}{2}\Leftrightarrow x=-2\)

 

Answer 3

\(D=\dfrac{2x+1}{x^2+2}=\dfrac{\left(x^2+2\right)-\left(x^2-2x+1\right)}{x^2+2}=1-\dfrac{\left(x-1\right)^2}{x^2+2}\le1\)

\(D_{max}=1\Leftrightarrow x=1\)