Tìm Min?

M

microwavest

-------------------

ta có:

$\dfrac{x^2+4x}{3x^2+1}$

\Leftrightarrow$\dfrac{4x^2+4x+1-3x^2-1}{3x^2+1}$

\Leftrightarrow$\dfrac{(2x+1)^2}{3x^2+1}$$-1$ \geq $-1$

Vậy Min=$-1$ \Leftrightarrow $x=-\dfrac{1}{2}$
 
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