Question

$5 - (x + 3)(x - 1) = 2x + 8$
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Answer 1

$\sf{5-(x+3)(x-1)=2x+8}\\\sf{5-(x^2-x+3x-3)=2x+8}\\\sf{5-(x^2+2x-3)-2x-8=0}\\\sf{5-x^2-2x+3-2x-8=0}\\\sf{-x^2-4x+\diagup\!\!\!\!8-\diagup\!\!\!\!8=0}\\\sf{-x^2-4x=0\cdot(-1)}\\\sf{x^2+4x=0}\\\sf{x\cdot(x+4)=0}\\\sf{x=0}\\\sf{x+4=0}\\\sf{x=-4}$  

$\huge\boxed{\boxed{\boxed{\boxed{\sf{S=\{0,-4\}}}}}}$  

$\sf{\underline{Outra~resoluc_{\!\!,}\tilde{a}o:}}$  

$\sf{x^2+4x=0}\\\sf{a=1~~b=4~~c=0}\\\sf{\Delta=b^2-4ac}\\\sf{\Delta=4^2-4\cdot1\cdot0}\\\sf{\Delta=16}\\\sf{x=\dfrac{-b\pm\sqrt{\Delta}}{2a}}\\\sf{x=\dfrac{-4\pm\sqrt{16}}{2\cdot1}}\\\sf{x=\dfrac{-4\pm4}{2}}\begin{cases}\sf{x_1=\dfrac{-4+4}{2}=\dfrac{0}{2}=0}\\\sf{x_2=\dfrac{-4-4}{2}=-\dfrac{8}{2}=-4}\end{cases}$  

$\huge\boxed{\boxed{\boxed{\boxed{\sf{S=\{0,-4\}}}}}}$