Find the 9th term of the geometric sequence 5, -25, 125, ...
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so... if you notice, the vertex is at h,k and that'd be the origin, 0,0
so...since the directrix is "p" units from the vertex, so it'd be 2 units from 0,0
now, the parabola has an equation with a positive leading term's coefficient, namely the 1/8 is positive, thus, the parabola is opening upwards, and the directrix is "outside" the parabola, so is below the vertex
that puts the directrix 2 units below 0,0
y = -2