What is the directrix-2x^2+4x-9 ?

The directrix-2x^2+4x-9 is y=-55/8

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular >

directrix-2x^2+4x-9

directrix

- 2 x^{2} + 4 x - 9

y = - \frac{55}{8}

Solution steps

Rewrite

y = - 2 x^{2} + 4 x - 9

in the standard form

4 (- \frac{1}{8}) (y - (- 7)) = (x - 1)^{2}

(h, k) = (1, - 7), p = - \frac{1}{8}

Parabola is symmetric around the y-axis and so the directrix is a line parallel to the x-axis, a distance

- p

from the center

(1, - 7)

y-coordinate

y = - 7 - p

y = - 7 - (- \frac{1}{8})

Refine

y = - \frac{55}{8}

y = - \frac{1}{12} x^{2}

\frac{40 x ^{3}}{3 x}

(x - 3)^{2} = - 4 (y + 1)

y = x^{2} - 3 x^{2}

- 2 x^{2} - 4 x + y + 70 = 0