L
lovelybaby92


ta có : a = \frac{-x^3 + 4}{x^2} = f(x)
f'(x) = -1 - \frac{8}{x^3}
f'(x) = 0 \Leftrightarrow \frac{8}{x^3} = -1
\Leftrightarrow x = -2
f'(x) = -1 - \frac{8}{x^3}
f'(x) = 0 \Leftrightarrow \frac{8}{x^3} = -1
\Leftrightarrow x = -2