Resposta:
a) S = {12, 6}
b) S = {-1, -9}
Explicação passo a passo:
a)
[tex]\triangle=b^2-4ac\\\triangle=(-18)^2-4*1*72\\\triangle=324-288\\\triangle=36\\[/tex]
[tex]\displaystyle x=\frac{-b\pm\sqrt{\triangle}}{2a}[/tex]
[tex]\displaystyle x=\frac{-(-18)\pm\sqrt{36}}{2*1}[/tex]
[tex]\displaystyle x=\frac{18\pm6}{2}[/tex]
[tex]\displaystyle x1=\frac{18+6}{2}[/tex]
[tex]\displaystyle x2=\frac{18-6}{2}[/tex]
[tex]\displaystyle x1 = 12\\x2 = 6[/tex]
b)
[tex]a = 1, b = 10, c = 9\\\triangle=b^2-4ac\\\triangle=10^2-4*1*9\\\triangle=100-36\\\triangle=64\\[/tex]
[tex]\displaystyle x=\frac{-b\pm\sqrt{\triangle}}{2a}[/tex]
[tex]\displaystyle x=\frac{-10\pm\sqrt{64}}{2*1}[/tex]
[tex]\displaystyle x=\frac{-10\pm8}{2}[/tex]
[tex]\displaystyle x1=\frac{-10+8}{2}[/tex]
[tex]\displaystyle x2=\frac{-10-8}{2}[/tex]
[tex]\displaystyle x1=-1\\x2 =-9[/tex]
