Resposta:
b) -4 e 7
Explicação passo a passo:
[tex]a = 1, b = -3, c = -28\\\triangle=b^2-4ac\\\triangle=(-3)^2-4*1*(-28)\\\triangle=9+112\\\triangle=121\\[/tex]
[tex]\displaystyle x=\frac{-b\pm\sqrt{\triangle}}{2a}[/tex]
[tex]\displaystyle x=\frac{-(-3)\pm\sqrt{121}}{2*1}[/tex]
[tex]\displaystyle x=\frac{3\pm11}{2}[/tex]
[tex]\displaystyle x1=\frac{3+11}{2}[/tex]
[tex]\displaystyle x2=\frac{3-11}{2}[/tex]
[tex]\displaystyle x1=7\\x2=-4[/tex]
