[tex]\Box \ \ \boxed{\begin{array}{l}\sf -7x^2+28=0 \end{array}}\\\\\\a=-7\\b=28\\c=0\\\\\\[/tex]
[tex]\Box \ \ \boxed{\begin{array}{l}\sf -7x^2+28=0 \end{array}}\\\\Retira \ o \ sinal \ de \ negativo \ do \ primeiro \ termo\\\\\Box \ \ \boxed{\begin{array}{l}\sf -7x^2+28=0 \ .(-1) \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf 7x^2-28=0 \end{array}}\\\\[/tex]
[tex]Podemos \ dividir \ por \ 7, \ n\~ao \ altera \ o \ resultado\\\\\Box \ \ \boxed{\begin{array}{l}\sf 7x^2 + 28 =\frac{0}{7} \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x^2-4=0 \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x^2=4 \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x=\pm\sqrt{4} \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x'=-2 \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x''=2 \end{array}}\\[/tex]
[tex]\Box \ \ \boxed{\begin{array}{l}\sf S = \{-2, 2\} \end{array}}[/tex]
resposta correta;
O conjunto ''R'' Real
da equação é;
[tex]\Box \ \ \boxed{\begin{array}{l}\sf S = \{-2, 2\} \end{array}}[/tex]
[tex]\ \ \ \ \heartsuit\\|\underline{\overline{\mathcal{\boldsymbol{\LaTeX}}}}|[/tex]
