What is the directrix y=x^2+8x-5 ?

The directrix y=x^2+8x-5 is y=-85/4

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

directrix y=x^2+8x-5

directrix

y = - \frac{85}{4}

Solution steps

Rewrite

y = x^{2} + 8 x - 5

in the standard form

4 \cdot \frac{1}{4} (y - (- 21)) = (x - (- 4))^{2}

(h, k) = (- 4, - 21), p = \frac{1}{4}

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

(- 4, - 21)

y-coordinate

y = - 21 - p

y = - 21 - \frac{1}{4}

Refine

y = - \frac{85}{4}