Question

Find an equation of a parabola with a vertex at the origin and directrix y = –3.5
A. y = –start fraction 1 over 14 end fractionx2
B. y = start fraction 1 over 14 end fractionx2
C. x = start fraction 1 over 14 end fractiony2
D. x = –start fraction 1 over 14 end fractiony2

Answer 1

x^2 = 4py has directrix at y = -p
so p = 7/2
x^2 = 14y
or
y = 1/14 x^2

Answer 2

The correct answer is B. y = start fraction 1 over 14 end fractionx2.