Mathematic Problems
366. példa

Solve the following inequality on the set of real numbers!

${x}^{2}-x-2=0$

${x}_{1,2}=\frac{-\left(-1\right)±\sqrt{{\left(-1\right)}^{2}-4·1·\left(-2\right)}}{2·1}$
${x}_{1,2}=\frac{1±\sqrt{1+8}}{2}$
${x}_{1,2}=\frac{1±\sqrt{9}}{2}$
${x}_{1,2}=\frac{1±3}{2}$


$x\in \left[-1,2\right]$