Question

${x }^{2} - 3x - 18 = 0$
qual o valor desse número? ​

Answer 1

$\Large\mathsf\displaystyle{} {x}^{2} - 3x - 18 = 0 \\\\\Large\mathsf\displaystyle{} \begin{cases}a = 1 \\ b = - 3 \\ c = - 18\end{cases} \\\\ \Large\mathsf\displaystyle{}x = \dfrac{ -\left( - 3\right) \pm \sqrt{\left( - 3\right)^{2} - 4\cdot1\cdot\left( - 18\right)} }{2\cdot1} \\\\\Large\mathsf\displaystyle{}x = \dfrac{3 \pm \sqrt{9 + 72} }{2} \\\\\Large\mathsf\displaystyle{}x = \dfrac{3 \pm \sqrt{81} }{2} \\\\\\ \Large\mathsf\displaystyle{}x = \dfrac{3 \pm9}{2} \\\\\Large\mathsf\displaystyle{}x = \dfrac{3 + 9}{2} \\\\\Large\mathsf\displaystyle{}x = \dfrac{3 - 9}{2} \\\\\\\Large\mathsf\displaystyle{} x = 6 \\ \Large\mathsf\displaystyle{}x = - 3$

Solução:

$\Large\displaystyle\text{ \begin{gathered} \underline{\boxed{\boldsymbol{ x_{1} = - 3 }}}\end{gathered} }$

$\Large\displaystyle\text{ \begin{gathered} \underline{\boxed{\boldsymbol{ x_{2} = 6 }}}\end{gathered} }$

$\Large\mathsf\displaystyle{}\displaystyle\text{ \begin{gathered} \underline{\boxed{\boldsymbol{{ \red{Bons}} \blue{\:Estudos}}}}\end{gathered} }$