Question

Quais as coordenadas do vértice V (xv,yv) da função dada por y= -2x^2-6x+8 ?
A) (4,0)
B) (4,1)
C) (12,5;-1)
D) (-1;12,5)

Answer 1

As coordenada do vértice de uma função do 2° grau são dadas por:

$Vertice:\;\left(V_x\,,\,V_y\right)\,=\,\left(-\frac{b}{2a}\;,\;-\frac{\Delta}{4a}\right)$

Vamos então determina-lo:

     $Vertice:\;\left(V_x\,,\,V_y\right)\,=\,\left(-\frac{b}{2a}\;,\;-\frac{\Delta}{4a}\right)\\\\\\Vertice:\;\left(V_x\,,\,V_y\right)\,=\,\left(-\frac{-6}{2\,.\,(-2)}\;,\;-\frac{(-6)^2-4.(-2).8}{4\,.\,(-2)}\right)\\\\\\Vertice:\;\left(V_x\,,\,V_y\right)\,=\,\left(-\frac{-6}{-4}\;,\;-\frac{36+64}{-8}\right)\\\\\\Vertice:\;\left(V_x\,,\,V_y\right)\,=\,\left(-1\;,\;-\frac{100}{-8}\right)\\\\\\Vertice:\;\left(V_x\,,\,V_y\right)\,=\,\left(-1\;,\;12,5\right)$

Resp: Letra D