Exercício Resolvido de Inequações
b)
\( x^{2}-x-1\leqslant 0 \)
\[
\begin{gathered}
x^{2}-x-1=0\\[5pt]
\Delta=b^{2}-4ac=(-1)^{2}-4.1.(-1)=1+4=5\\[5pt]
t=\frac{-b\pm\sqrt{\Delta \;}}{2a}=\frac{-(-1)\pm \sqrt{5\;}}{2.1}=\frac{1\pm\sqrt{5\;}}{2}\\[5pt]
x=\frac{1-\sqrt{5\;}}{2}\qquad \text{ou}\qquad x=\frac{1+\sqrt{5\;}}{2}
\end{gathered}
\]
\[ \bbox[#FFCCCC,10px]
{V=\left[\frac{1-\sqrt{5\;}}{2};\frac{1+\sqrt{5\;}}{2}\right]}
\]