Question

conjunto R da equaçao -7x^2+28=0

Answer 1

$\Box \ \ \boxed{\begin{array}{l}\sf -7x^2+28=0 \end{array}}\\\\\\a=-7\\b=28\\c=0$

$\Box \ \ \boxed{\begin{array}{l}\sf -7x^2+28=0 \end{array}}\\\\Retira \ o \ sinal \ de \ negativo \ do \ primeiro \ termo\\\\\Box \ \ \boxed{\begin{array}{l}\sf -7x^2+28=0 \ .(-1) \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf 7x^2-28=0 \end{array}}$

$Podemos \ dividir \ por \ 7, \ n\~ao \ altera \ o \ resultado\\\\\Box \ \ \boxed{\begin{array}{l}\sf 7x^2 + 28 =\frac{0}{7} \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x^2-4=0 \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x^2=4 \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x=\pm\sqrt{4} \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x'=-2 \end{array}}\\\Box \ \ \boxed{\begin{array}{l}\sf x''=2 \end{array}}$

$\Box \ \ \boxed{\begin{array}{l}\sf S = \{-2, 2\} \end{array}}$

resposta correta;

O conjunto ''R''  Real

da equação é;

$\Box \ \ \boxed{\begin{array}{l}\sf S = \{-2, 2\} \end{array}}$

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Answer 2

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$\large\boxed{\begin{array}{l}\sf\!-7x^2+28=0\\\sf 7x^2=28\\\sf x^2=\dfrac{28}{7}\\\sf x^2=4\\\sf x=\pm\sqrt{4}\\\sf x=\pm2\\\sf S=\{-2,2\}\end{array}}$