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Rezovati in R ecuatia : x+radical din x de ordinul 3 +2 =0

Răspuns :

   
[tex]\displaystyle\\ x+ \sqrt[3]{x} +2 =0\\\\ \texttt{Notatie:} ~~x=y^3\\\\ y^3+ \sqrt[3]{y^3}+2=0\\\\ y^3+y+2=0\\\\ \text{Observam ca }~y=-1~\text{ este solutie a ecuatiei.}\\\\ \text{Rezulta ca il putem scoate factorul: }~(y+1)\\\\ y^3+y+2=0\\\\ y^3+\underbrace{y^2-y^2-y+y} +y+2 =0\\\\ y^3+y^2-y^2-y+2y+2 =0\\\\ y^2(y+1)-y(y+1) + 2(y+1)=0\\\\ (y+1)(y^2-y+2)=0\\ \\ y-1=0~~~\Longrightarrow~~y_1=-1 \\\\ y^2-y+2)=0~~\Delta=1-8=-7\ \textless \ 0~~\Longrightarrow~~y\notin R[/tex]


[tex]\Longrightarrow~~~\texttt{ Solutie unica: }~\boxed{y = -1} \\ \\ \text{Revenim la x, necunoscuta initiala.}\\\\ \bold{x = y^3 = (-1)^3 = \boxed{\boxed{\bold{-1}}}} [/tex]