What is the directrix y=x^2-8x+7 ?

The directrix y=x^2-8x+7 is y=-37/4

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directrix y=x^2-8x+7

directrix

y = x^{2} - 8 x + 7

y = - \frac{37}{4}

Solution steps

Rewrite

y = x^{2} - 8 x + 7

in the standard form

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

(h, k) = (4, - 9), 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, - 9)

y-coordinate

y = - 9 - p

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

Refine

y = - \frac{37}{4}

y = \frac{x ( x + 5 )}{7}

x^{2} + 9 x + 20

y = - 7 x^{2} - 3

x^{2} - 10

y^{2} + 36 x = 0