[tex]\displaystyle (x+4)^2=9 \\ x^2+2 \cdot x \cdot 4+4^2=9 \\ x^2+8x+16=9 \\ x^2+8x+16-9=0 \\ x^2+8x+7=0 \\ a=1,b=8,c=7 \\ \Delta=b^2-4ac=8^2-4 \cdot 1 \cdot 7=64-28=36\ \textgreater \ 0 \\ x_1= \frac{-8+ \sqrt{36} }{2 \cdot 1} = \frac{-8+6}{2} = \frac{-2}{2} =-1 \\ \\ x_2= \frac{-8- \sqrt{36} }{2 \cdot 1} = \frac{-8-6}{2} = \frac{-14}{2} =-7[/tex]
