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

The directrix 2x^2-4x-9 is y=-89/8

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{89}{8}

Solution steps

Rewrite

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

in the standard form

4 \cdot \frac{1}{8} (y - (- 11)) = (x - 1)^{2}

(h, k) = (1, - 11), 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, - 11)

y-coordinate

y = - 11 - p

y = - 11 - \frac{1}{8}

Refine

y = - \frac{89}{8}

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

x^{2} = 4 y + 8

\frac{9 x ^{2}}{2}

2 x^{2} + 8 x + 13

2 x^{2} - 4 x + 9