What is the directrix (x-2)(x+1) ?

The directrix (x-2)(x+1) is y=-5/2

English

Español

Português

Français

Deutsch

Italiano

Русский

中文(简体)

한국어

日本語

Tiếng Việt

עברית

العربية

Popular >

directrix (x-2)(x+1)

directrix

(x - 2) (x + 1)

y = - \frac{5}{2}

Solution steps

Rewrite

y = (x - 2) (x + 1)

in the standard form

4 \cdot \frac{1}{4} (y - (- \frac{9}{4})) = (x - \frac{1}{2})^{2}

(h, k) = (\frac{1}{2}, - \frac{9}{4}), 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

(\frac{1}{2}, - \frac{9}{4})

y-coordinate

y = - \frac{9}{4} - p

y = - \frac{9}{4} - \frac{1}{4}

Refine

y = - \frac{5}{2}

5 x^{2} + 30 x + 24 y = 51

x^{2} - 2 x - 4 y + 9 = 0

\frac{- 3 x ^{2} - 2 x + 6}{5}

3 x^{2} - x - 2

y = - 3 x^{2} - 12 x - 9