Question 39: The function \(y=-x^3+3x+5\) covariates on which of the following intervals

TXĐ \(D=\mathbb{R}\)

\(y’=-3x^2+3\)

\(y’=0\Leftrightarrow -3x^2+3=0\) \( \Leftrightarrow \left[\begin{array}{l}x=-1\\x=1\end{array}\right\)

The variation table has the form

So the above covariate function (-1;1)

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