Question

Quais dos pontos pertencem à parábola y=x -2x-3?
a) (0,-3)
b) (1,-4)
c) (1,-3)
d) (2,-3)
e) (3,0)
f) (4,-3)

Answer 1

a = 1, b = -2, c = -3

$\Delta = b^2 - 4 * a * c \\ \Delta = (-2)^2 - 4 * 1 * (-3) \\ \Delta = 4 + 12 \\ \Delta = 16 \\ \\ X_v = - \frac{b}{2*a} \\ X_v = - \frac{(-2)}{2*1} \\ X_v = \frac{2}{2} \\ X_v = 1 \\ \\ Y_v = - \frac{\Delta}{4*a} \\ Y_v = - \frac{16}{4*1} \\ Y_v = \frac{-16}{4} \\ Y_v = -4$

X = 1;
Y = -4.

Logo a alternativa correta é a letra B).