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Find all rational zeros of f. Then use the depressed equation to find all roots of the question f(x)=0

6x^3-11x-9x-1

Find all rational zeros of f Then use the depressed equation to find all roots of the question fx0 6x311x9x1 class=

Respuesta :

[tex]\bf 6x^3-11x^2-9x-1=0 \qquad \begin{array}{lllrrrll} -\frac{1}{2}&|&6&-11&-9&-1\\ &|&&-3&7&1\\ \textendash\textendash\textendash&|&\textendash\textendash\textendash&\textendash\textendash\textendash&\textendash\textendash\textendash&\textendash\textendash\textendash\\ &&6&-14&-2&0 \end{array} \\\\ \\\\ x=-\frac{1}{2}\implies x+\frac{1}{2}=0\implies \left( x+\frac{1}{2} \right)(6x^2-14x-2)=0 \\\\ \textit{taking common factor on the quadratic} \\\\ [/tex][tex]\bf \left( x+\frac{1}{2} \right)2(3x^2-7x-1)=0\implies \left( x+\frac{1}{2} \right)(3x^2-7x-1)=0 \\\\ \textit{doing the quadratic formula on it} \\\\ x=\cfrac{-(-7)\pm\sqrt{(-7)^2-4(3)(-1)}}{2(3)} \\\\\\ x=\cfrac{7\pm\sqrt{49+12}}{6}\implies x=\cfrac{7\pm\sqrt{61}}{6}\impliedby \textit{61 is a prime number} \\\\\\ thus\implies x\to \begin{cases} -\frac{1}{2} \\\\ \cfrac{7+\sqrt{61}}{6} \\\\ \cfrac{7-\sqrt{61}}{6} \end{cases}[/tex]