Question

como resolver a função do 2º grau y= x²-2x-8?

Answer 1

$f(x) = x^2-2x-8\\ a=1\ \ \ \ \ b =-2\ \ \ \ \ c =-8\\ \Delta=b^2-4ac\\ \Delta=(-2)^2-4\cdot1\cdot(-8)\\ \Delta=4+32\\ \Delta=36\\ \\ x=\frac{-b\pm\sqrt{\Delta}}{2\cdot a}=\frac{-(-2)\pm\sqrt{36}}{2\cdot 1}=\frac{2\pm6}{2}\\ \\x'=\frac{2+6}{2}=\frac{8}{2}=4\\ \\x''=\frac{2-6}{2}=\frac{-4}{2}=-2\\ \\S=\{-2, \ 4\}$

$x_V=-\frac{b}{2a}=-\frac{-2}{2\cdot1}=-\frac{-2}{2}=-(-1)=1\\ \\ y_V=-\frac{\Delta}{4a}=-\frac{36}{4\cdot 1}=\frac{36}{4}=-9$

Answer 2

espero ter ajudado........................