Question

Resolva a equação do 2º grau: x2 + 6x - 7 = 0,marque a alternativa correta. a) ( )x= -6 ou x = 2 b)( ) x = - 8 ou x = -4 c) ( )x= - 5 ou x= 3 d) ( )...

Answer 1

$x^2+6x-7=0\rightarrow\begin{cases}a=1~\\b=6\\c=-7\\\end{cases}$

$\boxed{\begin{array}{lr} \Delta=b^2-4.a.c\\\Delta=6^2-4.1.-7\\\Delta=36-4.1.-7\\\Delta=36+28\\\Delta=64\ \ \ \checkmark \end{array}}$

$\boxed{\begin{array}{lr} x=\frac{-b\pm\sqrt{\Delta}}{2.a} \\\\x=\frac{-6\pm\sqrt{64}}{2.1}\\\\x=\frac{-6\pm8}{2}\\\\------\\\\x'=\frac{-6+8}{2}\\\\x'=\frac{2}{2}\\\\x'=1\ \ \checkmark\\\\------\\\\x''=\frac{-6-8}{2}\\\\x''=\frac{-14}{2}\\\\x''=-7\ \ \checkmark\end{array}}$

$S=\{1,-7\}$

Resposta;

d)

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